diff --git a/drools-drl/drools-drl-parser-tests/src/test/java/org/drools/drl/parser/antlr4/MiscDRLParserTest.java b/drools-drl/drools-drl-parser-tests/src/test/java/org/drools/drl/parser/antlr4/MiscDRLParserTest.java
index ab2f7070606..875315157d1 100644
--- a/drools-drl/drools-drl-parser-tests/src/test/java/org/drools/drl/parser/antlr4/MiscDRLParserTest.java
+++ b/drools-drl/drools-drl-parser-tests/src/test/java/org/drools/drl/parser/antlr4/MiscDRLParserTest.java
@@ -2174,12 +2174,44 @@ public void parse_QualifiedClassname() throws Exception {
     }
 
     @Test
-    public void parse_Accumulate() throws Exception {
-        final PackageDescr pkg = parseAndGetPackageDescrFromFile(
-                                                               "accumulate.drl" );
+    void accumulate() {
+        final String drl = "rule R\n" +
+                "when\n" +
+                "     accumulate( Person( $age : age );\n" +
+                "                 $avg : average( $age ) );\n" +
+                "then\n" +
+                "end";
+        RuleDescr rule = parseAndGetFirstRuleDescr(drl);
+
+        PatternDescr out = (PatternDescr) rule.getLhs().getDescrs().get( 0 );
+        assertThat(out.getObjectType()).isEqualTo("Object");
+        AccumulateDescr accum = (AccumulateDescr) out.getSource();
+        assertThat(accum.isExternalFunction()).isTrue();
+
+        List<AccumulateDescr.AccumulateFunctionCallDescr> functions = accum.getFunctions();
+        assertThat(functions.size()).isEqualTo(1);
+        assertThat(functions.get(0).getFunction()).isEqualTo("average");
+        assertThat(functions.get(0).getBind()).isEqualTo("$avg");
+        assertThat(functions.get(0).getParams()[0]).isEqualTo("$age");
+
+        final PatternDescr pattern = accum.getInputPattern();
+        assertThat(pattern.getObjectType()).isEqualTo("Person");
+
+        // accum.getInput() is always AndDescr
+        assertThat(accum.getInput()).isInstanceOfSatisfying(AndDescr.class, and -> {
+            assertThat(and.getDescrs()).hasSize(1);
+            assertThat(and.getDescrs().get(0)).isInstanceOfSatisfying(PatternDescr.class, patternDescr -> {
+                assertThat(patternDescr.getObjectType()).isEqualTo("Person");
+            });
+        });
+    }
+
+    @Test
+    void fromAccumulate() {
+        final PackageDescr pkg = parseAndGetPackageDescrFromFile("from_accumulate.drl" );
 
         assertThat(pkg.getRules().size()).isEqualTo(1);
-        final RuleDescr rule = (RuleDescr) pkg.getRules().get( 0 );
+        final RuleDescr rule = pkg.getRules().get( 0 );
         assertThat(rule.getLhs().getDescrs().size()).isEqualTo(1);
 
         final PatternDescr outPattern = (PatternDescr) rule.getLhs().getDescrs().get( 0 );
@@ -2191,8 +2223,16 @@ public void parse_Accumulate() throws Exception {
 
         assertThat(accum.isExternalFunction()).isFalse();
 
-        final PatternDescr pattern = (PatternDescr) accum.getInputPattern();
+        final PatternDescr pattern = accum.getInputPattern();
         assertThat(pattern.getObjectType()).isEqualTo("Person");
+
+        // accum.getInput() is always AndDescr
+        assertThat(accum.getInput()).isInstanceOfSatisfying(AndDescr.class, and -> {
+            assertThat(and.getDescrs()).hasSize(1);
+            assertThat(and.getDescrs().get(0)).isInstanceOfSatisfying(PatternDescr.class, patternDescr -> {
+                assertThat(patternDescr.getObjectType()).isEqualTo("Person");
+            });
+        });
     }
 
     @Test
@@ -5232,4 +5272,36 @@ void durationChunk() {
         // At the moment, the parser accepts any input and let the compile phase validate it.
         assertThat(rule.getAttributes().get("duration").getValue()).isEqualTo("wrong input");
     }
+
+    @Test
+    void accumulateWithEmptyActionAndReverse() {
+        final String drl = "rule R when\n" +
+                "    Number() from accumulate( Number(),\n" +
+                "        init( double total = 0; ),\n" +
+                "        action( ),\n" +
+                "        reverse( ),\n" +
+                "        result( new Double( total ) )\n" +
+                "    )\n" +
+                "then end";
+        RuleDescr rule = parseAndGetFirstRuleDescr(drl);
+
+        final PatternDescr outPattern = (PatternDescr) rule.getLhs().getDescrs().get( 0 );
+        final AccumulateDescr accum = (AccumulateDescr) outPattern.getSource();
+        assertThat(accum.getInitCode()).isEqualTo( "double total = 0;");
+        assertThat(accum.getActionCode()).isEmpty();
+        assertThat(accum.getReverseCode()).isEmpty();
+        assertThat(accum.getResultCode()).isEqualTo( "new Double( total )");
+
+        assertThat(accum.isExternalFunction()).isFalse();
+
+        final PatternDescr pattern = accum.getInputPattern();
+        assertThat(pattern.getObjectType()).isEqualTo("Number");
+
+        assertThat(accum.getInput()).isInstanceOfSatisfying(AndDescr.class, and -> {
+            assertThat(and.getDescrs()).hasSize(1);
+            assertThat(and.getDescrs().get(0)).isInstanceOfSatisfying(PatternDescr.class, patternDescr -> {
+                assertThat(patternDescr.getObjectType()).isEqualTo("Number");
+            });
+        });
+    }
 }
diff --git a/drools-drl/drools-drl-parser-tests/src/test/resources/org/drools/drl/parser/antlr4/accumulate.drl b/drools-drl/drools-drl-parser-tests/src/test/resources/org/drools/drl/parser/antlr4/from_accumulate.drl
similarity index 100%
rename from drools-drl/drools-drl-parser-tests/src/test/resources/org/drools/drl/parser/antlr4/accumulate.drl
rename to drools-drl/drools-drl-parser-tests/src/test/resources/org/drools/drl/parser/antlr4/from_accumulate.drl
diff --git a/drools-drl/drools-drl-parser/src/main/antlr4/org/drools/drl/parser/antlr4/DRLParser.g4 b/drools-drl/drools-drl-parser/src/main/antlr4/org/drools/drl/parser/antlr4/DRLParser.g4
index cf1afb97862..cabdaaa1f34 100644
--- a/drools-drl/drools-drl-parser/src/main/antlr4/org/drools/drl/parser/antlr4/DRLParser.g4
+++ b/drools-drl/drools-drl-parser/src/main/antlr4/org/drools/drl/parser/antlr4/DRLParser.g4
@@ -340,7 +340,8 @@ fromAccumulate := ACCUMULATE LEFT_PAREN lhsAnd (COMMA|SEMICOLON)
                         ) RIGHT_PAREN
 */
 fromAccumulate : (DRL_ACCUMULATE|DRL_ACC) LPAREN lhsAndDef (COMMA|SEMI)
-                   ( DRL_INIT LPAREN initBlockStatements=chunk? RPAREN COMMA? DRL_ACTION LPAREN actionBlockStatements=chunk? RPAREN COMMA? ( DRL_REVERSE LPAREN reverseBlockStatements=chunk? RPAREN COMMA?)? DRL_RESULT LPAREN resultBlockStatements=chunk RPAREN
+                   ( DRL_INIT LPAREN initBlockStatements=chunk? RPAREN COMMA? DRL_ACTION LPAREN actionBlockStatements=chunk? RPAREN COMMA? DRL_REVERSE LPAREN reverseBlockStatements=chunk? RPAREN COMMA? DRL_RESULT LPAREN resultBlockStatements=chunk RPAREN
+                   | DRL_INIT LPAREN initBlockStatements=chunk? RPAREN COMMA? DRL_ACTION LPAREN actionBlockStatements=chunk? RPAREN COMMA? DRL_RESULT LPAREN resultBlockStatements=chunk RPAREN
                    | accumulateFunction
                    )
                  RPAREN (SEMI)?
diff --git a/drools-drl/drools-drl-parser/src/main/java/org/drools/drl/parser/antlr4/DRLVisitorImpl.java b/drools-drl/drools-drl-parser/src/main/java/org/drools/drl/parser/antlr4/DRLVisitorImpl.java
index 39aa5e930e8..d67450e9193 100644
--- a/drools-drl/drools-drl-parser/src/main/java/org/drools/drl/parser/antlr4/DRLVisitorImpl.java
+++ b/drools-drl/drools-drl-parser/src/main/java/org/drools/drl/parser/antlr4/DRLVisitorImpl.java
@@ -699,7 +699,8 @@ public PatternDescr visitLhsAccumulate(DRLParser.LhsAccumulateContext ctx) {
         AccumulateDescr accumulateDescr = BaseDescrFactory.builder(new AccumulateDescr())
                 .withParserRuleContext(ctx)
                 .build();
-        accumulateDescr.setInput(visitLhsAndDef(ctx.lhsAndDef()));
+        // accumulateDescr.input is always AndDescr
+        accumulateDescr.setInput(wrapWithAndDescr(visitLhsAndDef(ctx.lhsAndDef()), ctx.lhsAndDef()));
 
         // accumulate function
         for (DRLParser.AccumulateFunctionContext accumulateFunctionContext : ctx.accumulateFunction()) {
@@ -714,6 +715,18 @@ public PatternDescr visitLhsAccumulate(DRLParser.LhsAccumulateContext ctx) {
         return patternDescr;
     }
 
+    private AndDescr wrapWithAndDescr(BaseDescr baseDescr, ParserRuleContext ctx) {
+        if (baseDescr instanceof AndDescr andDescr) {
+            return andDescr;
+        } else {
+            AndDescr andDescr = BaseDescrFactory.builder(new AndDescr())
+                    .withParserRuleContext(ctx)
+                    .build();
+            andDescr.addDescr(baseDescr);
+            return andDescr;
+        }
+    }
+
     @Override
     public Object visitLhsGroupBy(DRLParser.LhsGroupByContext ctx) {
         GroupByDescr groupByDescr = BaseDescrFactory.builder(new GroupByDescr())
@@ -775,7 +788,8 @@ public AccumulateDescr visitFromAccumulate(DRLParser.FromAccumulateContext ctx)
         AccumulateDescr accumulateDescr = BaseDescrFactory.builder(new AccumulateDescr())
                 .withParserRuleContext(ctx)
                 .build();
-        accumulateDescr.setInput(visitLhsAndDef(ctx.lhsAndDef()));
+        // accumulateDescr.input is always AndDescr
+        accumulateDescr.setInput(wrapWithAndDescr(visitLhsAndDef(ctx.lhsAndDef()), ctx.lhsAndDef()));
         if (ctx.DRL_INIT() != null) {
             // inline custom accumulate
             accumulateDescr.setInitCode(getTextPreservingWhitespace(ctx.initBlockStatements));