diff --git c/devel/avro-c/Makefile i/devel/avro-c/Makefile
index b359ea7c6eed..903483af57ff 100644
--- c/devel/avro-c/Makefile
+++ i/devel/avro-c/Makefile
@@ -14,11 +14,6 @@ COMMENT=	C library for Apache Avro
 LICENSE=	APACHE20
 LICENSE_FILE=	${WRKSRC}/LICENSE
 
-BROKEN_aarch64=	fails to build: error: No atomic implementation
-BROKEN_armv6=	fails to build: error: No atomic implementation
-BROKEN_armv7=	fails to build: error: No atomic implementation
-BROKEN_mips=	fails to build: error: No atomic implementation
-BROKEN_mips64=	fails to build: error: No atomic implementation
 BROKEN_sparc64=	fails to build
 
 LIB_DEPENDS=	libjansson.so:devel/jansson \
diff --git c/devel/avro-c/files/patch-src_avro_refcount.h i/devel/avro-c/files/patch-src_avro_refcount.h
new file mode 100644
index 000000000000..95273d0ca085
--- /dev/null
+++ i/devel/avro-c/files/patch-src_avro_refcount.h
@@ -0,0 +1,11 @@
+--- src/avro/refcount.h.orig	2018-08-09 12:31:39 UTC
++++ src/avro/refcount.h
+@@ -118,7 +118,7 @@ avro_refcount_dec(volatile int *refcount)
+  * GCC intrinsics
+  */
+ 
+-#elif (__GNUC__ * 10000 + __GNUC_MINOR__ * 100 + __GNUC_PATCHLEVEL__) > 40500
++#elif (__GNUC__ * 10000 + __GNUC_MINOR__ * 100 + __GNUC_PATCHLEVEL__) > 40500 || defined(__clang__)
+ 
+ static inline void
+ avro_refcount_set(volatile int *refcount, int value)