diff --git a/Jamrules b/Jamrules
index 75fce209d3..613e161936 100644
--- a/Jamrules
+++ b/Jamrules
@@ -81,12 +81,15 @@ C++FLAGS += -nostdinc ;
 # issues, they deprecated that nice function. This will enable it again:
 C++FLAGS += -D_ZETA_USING_DEPRECATED_API_=1 ;
 
+if ! $(TARGET_PLATFORM) {
+	ECHO "Variable TARGET_PLATFORM not set. Please run ./configure or" ;
+	EXIT "specify it manually." ;
+}
 switch $(TARGET_PLATFORM)
 {
 	case r5 :
 	{
-		CCFLAGS += -DCOMPILE_FOR_R5 ;
-		C++FLAGS += -DCOMPILE_FOR_R5 ;
+		# "everything" is r5 compatible
 	}
 	case bone : 
 	{