diff --git a/modules/pythia/CMakeLists.txt b/modules/pythia/CMakeLists.txt
index 5f094400856050e253762403714f508434bacd98..9770c4fc2b22cb0f2841a6295717c510d4376b9a 100644
--- a/modules/pythia/CMakeLists.txt
+++ b/modules/pythia/CMakeLists.txt
@@ -28,7 +28,7 @@ if ("x_${USE_PYTHIA8_C8}" STREQUAL "x_SYSTEM")
     IMPORTED_LOCATION ${Pythia8_LIBRARY}/libpythia8.a
     IMPORTED_LINK_INTERFACE_LIBRARIES dl
     INTERFACE_INCLUDE_DIRECTORIES ${Pythia8_INCLUDE_DIR}
-    INTERFACE_COMPILE_DEFINITIONS CORSIKA_Pythia8_PREFIX="${Pythia8_PREFIX}"
+    INTERFACE_COMPILE_DEFINITIONS CORSIKA_Pythia8_PREFIX=\"${Pythia8_PREFIX}\"
     )
   set (Pythia8_FOUND 1 PARENT_SCOPE)
 
@@ -71,7 +71,7 @@ else ()
     IMPORTED_LOCATION ${Pythia8_LIBRARY}
     IMPORTED_LINK_INTERFACE_LIBRARIES dl
     INTERFACE_INCLUDE_DIRECTORIES ${Pythia8_INCLUDE_DIR}
-    INTERFACE_COMPILE_DEFINITIONS CORSIKA_Pythia8_PREFIX="${Pythia8_PREFIX}"
+    INTERFACE_COMPILE_DEFINITIONS CORSIKA_Pythia8_PREFIX=\"${Pythia8_PREFIX}\"
     )
 
     message (STATUS "Pythia8 build at ${INSTALL_DIR}, final install to ${Pythia8_INSTALL_DIR}")