diff --git a/tcg/tcg-op-gvec.c b/tcg/tcg-op-gvec.c
index 78ee1ced80..97e4df221a 100644
--- a/tcg/tcg-op-gvec.c
+++ b/tcg/tcg-op-gvec.c
@@ -88,7 +88,20 @@ uint32_t simd_desc(uint32_t oprsz, uint32_t maxsz, int32_t data)
     uint32_t desc = 0;
 
     check_size_align(oprsz, maxsz, 0);
-    tcg_debug_assert(data == sextract32(data, 0, SIMD_DATA_BITS));
+
+    /*
+     * We want to check that 'data' will fit into SIMD_DATA_BITS.
+     * However, some callers want to treat the data as a signed
+     * value (which they can later get back with simd_data())
+     * and some want to treat it as an unsigned value.
+     * So here we assert only that the data will fit into the
+     * field in at least one way. This means that some invalid
+     * values from the caller will not be detected, e.g. if the
+     * caller wants to handle the value as a signed integer but
+     * incorrectly passes us 1 << (SIMD_DATA_BITS - 1).
+     */
+    tcg_debug_assert(data == sextract32(data, 0, SIMD_DATA_BITS) ||
+                     data == extract32(data, 0, SIMD_DATA_BITS));
 
     oprsz = (oprsz / 8) - 1;
     maxsz = (maxsz / 8) - 1;