Index: src/OFBlock.m
==================================================================
--- src/OFBlock.m
+++ src/OFBlock.m
@@ -24,10 +24,11 @@
 # import "OFAtomic.h"
 #endif
 #ifdef OF_HAVE_THREADS
 # import "OFPlainMutex.h"
 #endif
+#import "OFString.h"
 
 #import "OFAllocFailedException.h"
 #import "OFInitializationFailedException.h"
 
 #if defined(OF_OBJFW_RUNTIME)