diff --git a/src/freedreno/vulkan/tu_pipeline.c b/src/freedreno/vulkan/tu_pipeline.c
index 015873ac27a..ccfa9eb34e3 100644
--- a/src/freedreno/vulkan/tu_pipeline.c
+++ b/src/freedreno/vulkan/tu_pipeline.c
@@ -1136,8 +1136,13 @@ tu6_emit_vpc(struct tu_cs *cs,
       tu_cs_emit_pkt4(cs, REG_A6XX_PC_PRIMITIVE_CNTL_6, 1);
       tu_cs_emit(cs, A6XX_PC_PRIMITIVE_CNTL_6_STRIDE_IN_VPC(vec4_size));
 
+      uint32_t prim_size = prev_stage_output_size;
+      if (prim_size > 64)
+         prim_size = 64;
+      else if (prim_size == 64)
+         prim_size = 63;
       tu_cs_emit_pkt4(cs, REG_A6XX_SP_GS_PRIM_SIZE, 1);
-      tu_cs_emit(cs, prev_stage_output_size);
+      tu_cs_emit(cs, prim_size);
    }
 }