diff --git a/src/compiler/nir/nir_opt_load_store_vectorize.c b/src/compiler/nir/nir_opt_load_store_vectorize.c
index 04e5ffb79e6..be285e96767 100644
--- a/src/compiler/nir/nir_opt_load_store_vectorize.c
+++ b/src/compiler/nir/nir_opt_load_store_vectorize.c
@@ -681,6 +681,10 @@ new_bitsize_acceptable(struct vectorize_ctx *ctx, unsigned new_bit_size,
 
    unsigned high_offset = high->offset_signed - low->offset_signed;
 
+   /* This can cause issues when combining store data. */
+   if (high_offset % (new_bit_size / 8) != 0)
+      return false;
+
    /* check nir_extract_bits limitations */
    unsigned common_bit_size = MIN2(get_bit_size(low), get_bit_size(high));
    common_bit_size = MIN2(common_bit_size, new_bit_size);
diff --git a/src/compiler/nir/tests/load_store_vectorizer_tests.cpp b/src/compiler/nir/tests/load_store_vectorizer_tests.cpp
index 48dd1fb415f..633acc87824 100644
--- a/src/compiler/nir/tests/load_store_vectorizer_tests.cpp
+++ b/src/compiler/nir/tests/load_store_vectorizer_tests.cpp
@@ -755,6 +755,20 @@ TEST_F(nir_load_store_vectorize_test, ssbo_store_intersecting)
    ASSERT_EQ(nir_const_value_as_uint(cv[2], 32), 0x21);
 }
 
+TEST_F(nir_load_store_vectorize_test, gitlab_issue_12946)
+{
+   create_store(nir_var_mem_ssbo, 0, 0, 0x1, 32, 2, 0x3);
+   create_store(nir_var_mem_ssbo, 0, 3, 0x2, 32, 1, 0x1);
+
+   nir_validate_shader(b->shader, NULL);
+   ASSERT_EQ(count_intrinsics(nir_intrinsic_store_ssbo), 2);
+
+   /* The original issue was the crash when running the pass. */
+   EXPECT_TRUE(run_vectorizer(nir_var_mem_ssbo));
+
+   EXPECT_EQ(count_intrinsics(nir_intrinsic_store_ssbo), 2);
+}
+
 TEST_F(nir_load_store_vectorize_test, ssbo_store_identical)
 {
    create_store(nir_var_mem_ssbo, 0, 0, 0x1);