diff --git a/repos/hello_gpgpu/src/hello_gpgpu/benchmark/SURF/OpenSurf.cpp b/repos/hello_gpgpu/src/hello_gpgpu/benchmark/SURF/OpenSurf.cpp
index adc8f8db84..ee73760fb0 100644
--- a/repos/hello_gpgpu/src/hello_gpgpu/benchmark/SURF/OpenSurf.cpp
+++ b/repos/hello_gpgpu/src/hello_gpgpu/benchmark/SURF/OpenSurf.cpp
@@ -462,7 +462,7 @@ int main(int argc, char **argv)
 #endif
     /////////////////////////////////////////////////////////////////
 
-    unsigned int blockSize = 512; // max size of the thread blocks
+    unsigned int blockSize = 256; // 512; // max size of the thread blocks
     unsigned int sharedMemSize = 2 * blockSize;
 
     /*