diff --git a/modules/ocl/src/pyrlk.cpp b/modules/ocl/src/pyrlk.cpp
index a3e65dde3f..8e9420480c 100644
--- a/modules/ocl/src/pyrlk.cpp
+++ b/modules/ocl/src/pyrlk.cpp
@@ -142,7 +142,7 @@ static void lkSparse_run(oclMat &I, oclMat &J,
             int wave_size = queryDeviceInfo<WAVEFRONT_SIZE, int>(kernel);
             openCLSafeCall(clReleaseKernel(kernel));
 
-            static char opt[16] = {0};
+            static char opt[32] = {0};
             sprintf(opt, " -D WAVE_SIZE=%d", wave_size);
 
             openCLExecuteKernel(clCxt, &pyrlk, kernelName, globalThreads, localThreads,