diff --git a/intern/cycles/kernel/kernel_sse2.cpp b/intern/cycles/kernel/kernel_sse2.cpp
index 83f4b19ea9e..6f3f1714cbf 100644
--- a/intern/cycles/kernel/kernel_sse2.cpp
+++ b/intern/cycles/kernel/kernel_sse2.cpp
@@ -74,6 +74,7 @@ CCL_NAMESPACE_END
 #else
 
 /* needed for some linkers in combination with scons making empty compilation unit in a library */
-void __dummy_function_cycles_sse2(){}
+void __dummy_function_cycles_sse2(void);
+void __dummy_function_cycles_sse2(void){}
 
 #endif
diff --git a/intern/cycles/kernel/kernel_sse3.cpp b/intern/cycles/kernel/kernel_sse3.cpp
index 20c87960ae7..e6760981eef 100644
--- a/intern/cycles/kernel/kernel_sse3.cpp
+++ b/intern/cycles/kernel/kernel_sse3.cpp
@@ -75,6 +75,7 @@ CCL_NAMESPACE_END
 #else
 
 /* needed for some linkers in combination with scons making empty compilation unit in a library */
-void __dummy_function_cycles_sse3(){}
+void __dummy_function_cycles_sse3(void);
+void __dummy_function_cycles_sse3(void){}
 
 #endif
diff --git a/intern/cycles/kernel/kernel_sse41.cpp b/intern/cycles/kernel/kernel_sse41.cpp
index 31294ddc521..fd2198aebda 100644
--- a/intern/cycles/kernel/kernel_sse41.cpp
+++ b/intern/cycles/kernel/kernel_sse41.cpp
@@ -76,6 +76,7 @@ CCL_NAMESPACE_END
 #else
 
 /* needed for some linkers in combination with scons making empty compilation unit in a library */
-void __dummy_function_cycles_sse41(){}
+void __dummy_function_cycles_sse41(void);
+void __dummy_function_cycles_sse41(void){}
 
 #endif