diff --git a/source/ur/ur.hpp b/source/ur/ur.hpp
index cf84bb437d..2cddd11ff7 100644
--- a/source/ur/ur.hpp
+++ b/source/ur/ur.hpp
@@ -352,7 +352,8 @@ static inline void roundToHighestFactorOfGlobalSizeIn3d(
     size_t *ThreadsPerBlock, const size_t *GlobalSize,
     const size_t *MaxBlockDim, const size_t MaxBlockSize,
     const size_t WorkDim) {
-  ThreadsPerBlock[0] = std::min(GlobalSize[0], MaxBlockDim[0]);
+  ThreadsPerBlock[0] =
+      std::min(GlobalSize[0], std::min(MaxBlockSize, MaxBlockDim[0]));
   // Make the X dim a factor of 2
   do {
     roundToHighestFactorOfGlobalSize(ThreadsPerBlock[0], GlobalSize[0]);