diff --git a/Formula/g/graph-tool.rb b/Formula/g/graph-tool.rb
index 237900cf64f86..7d80f3399bc94 100644
--- a/Formula/g/graph-tool.rb
+++ b/Formula/g/graph-tool.rb
@@ -32,9 +32,9 @@ class GraphTool < Formula
   depends_on "gmp"
   depends_on "google-sparsehash"
   depends_on "gtk+3"
-  depends_on macos: :mojave # for C++17
   depends_on "libomp"
   depends_on "llvm"
+  depends_on macos: :mojave # for C++17
   depends_on "numpy"
   depends_on "pillow"
   depends_on "py3cairo"
@@ -137,7 +137,7 @@ def install
     ENV.deparallelize unless OS.mac?
 
     # Enable openmp
-    on_macos do
+    if OS.mac?
       ENV.append_to_cflags "-Xpreprocessor -fopenmp"
       ENV.append "LDFLAGS", "-L/usr/local/opt/libomp/lib -lomp"
       ENV.append "CPPFLAGS", "-I/usr/local/opt/libomp/include"