2 files changed, 3 insertions, 0 deletions
diff --git a/source/core/slang-gcc-compiler-util.cpp b/source/core/slang-gcc-compiler-util.cpp
index 3c4c4ec15..7838ca25b 100644
--- a/source/core/slang-gcc-compiler-util.cpp
+++ b/source/core/slang-gcc-compiler-util.cpp
@@ -511,6 +511,8 @@ static SlangResult _parseGCCFamilyLine(const UnownedStringSlice& line, LineParse
     for (const auto& define : options.defines)
     {
         StringBuilder builder;
+
+        builder << "-D";
         builder << define.nameWithSig;
         if (define.value.getLength())
         {
diff --git a/source/core/slang-visual-studio-compiler-util.cpp b/source/core/slang-visual-studio-compiler-util.cpp
index 3d0cfdc61..8b4598b43 100644
--- a/source/core/slang-visual-studio-compiler-util.cpp
+++ b/source/core/slang-visual-studio-compiler-util.cpp
@@ -204,6 +204,7 @@ namespace Slang
     for (const auto& define : options.defines)
     {
         StringBuilder builder;
+        builder << "/D";
         builder << define.nameWithSig;
         if (define.value.getLength())
         {