diff --git a/cmake/compiler/gcc/target_imacros.cmake b/cmake/compiler/gcc/target_imacros.cmake
index 804040411c5..0fba83819af 100644
--- a/cmake/compiler/gcc/target_imacros.cmake
+++ b/cmake/compiler/gcc/target_imacros.cmake
@@ -4,6 +4,12 @@
 
 macro(toolchain_cc_imacros header_file)
 
-  zephyr_compile_options(--imacros=${header_file})
+  # We cannot use the "-imacros foo" form here as CMake insists on
+  # deduplicating arguments, meaning that subsequent usages after the
+  # first one will see the "-imacros " part removed.
+  # gcc and clang support the "--imacros=foo" form but not xcc.
+  # Let's use the "combined" form (without space) which is supported
+  # by everyone so far.
+  zephyr_compile_options(-imacros${header_file})
 
 endmacro()