diff --git a/interface/gemmt.c b/interface/gemmt.c
index 018deb7fb..cae00877e 100644
--- a/interface/gemmt.c
+++ b/interface/gemmt.c
@@ -522,7 +522,7 @@ void CNAME(enum CBLAS_ORDER order, enum CBLAS_UPLO Uplo,
 
 			IDEBUG_START;
 
-			buffer_size = j + k + 128 / sizeof(FLOAT);
+			buffer_size = 2 * (j + k) + 128 / sizeof(FLOAT);
 #ifdef WINDOWS_ABI
 			buffer_size += 160 / sizeof(FLOAT);
 #endif
@@ -611,7 +611,7 @@ void CNAME(enum CBLAS_ORDER order, enum CBLAS_UPLO Uplo,
 #endif
 			IDEBUG_START;
 
-			buffer_size = j + k + 128 / sizeof(FLOAT);
+			buffer_size = 2 * (j + k) + 128 / sizeof(FLOAT);
 #ifdef WINDOWS_ABI
 			buffer_size += 160 / sizeof(FLOAT);
 #endif