diff --git a/src/hs_runtime.h b/src/hs_runtime.h
index 27de00a3..db52f4f5 100644
--- a/src/hs_runtime.h
+++ b/src/hs_runtime.h
@@ -250,7 +250,8 @@ hs_error_t hs_close_stream(hs_stream_t *id, hs_scratch_t *scratch,
  *      for future use and is unused at present.
  *
  * @param scratch
- *      A per-thread scratch space allocated by @ref hs_alloc_scratch().
+ *      A per-thread scratch space allocated by @ref hs_alloc_scratch(). This is
+ *      allowed to be NULL only if the @a onEvent callback is also NULL.
  *
  * @param onEvent
  *      Pointer to a match event callback function. If a NULL pointer is given,
@@ -299,7 +300,8 @@ hs_error_t hs_copy_stream(hs_stream_t **to_id, const hs_stream_t *from_id);
  *      The stream (as created by @ref hs_open_stream()) to be copied.
  *
  * @param scratch
- *      A per-thread scratch space allocated by @ref hs_alloc_scratch().
+ *      A per-thread scratch space allocated by @ref hs_alloc_scratch(). This is
+ *      allowed to be NULL only if the @a onEvent callback is also NULL.
  *
  * @param onEvent
  *      Pointer to a match event callback function. If a NULL pointer is given,
diff --git a/src/runtime.c b/src/runtime.c
index 66323789..335a83bc 100644
--- a/src/runtime.c
+++ b/src/runtime.c
@@ -1163,11 +1163,10 @@ hs_error_t hs_reset_and_copy_stream(hs_stream_t *to_id,
         return HS_INVALID;
     }
 
-    if (!scratch || !validScratch(to_id->rose, scratch)) {
-        return HS_INVALID;
-    }
-
     if (onEvent) {
+        if (!scratch || !validScratch(to_id->rose, scratch)) {
+            return HS_INVALID;
+        }
         report_eod_matches(to_id, scratch, onEvent, context);
     }
 
@@ -1406,12 +1405,14 @@ HS_PUBLIC_API
 hs_error_t hs_reset_stream(hs_stream_t *id, UNUSED unsigned int flags,
                            hs_scratch_t *scratch, match_event_handler onEvent,
                            void *context) {
-    if (!id || !scratch || !validScratch(id->rose, scratch)) {
+    if (!id) {
         return HS_INVALID;
     }
 
-    /* user wants eod matches */
     if (onEvent) {
+        if (!scratch || !validScratch(id->rose, scratch)) {
+            return HS_INVALID;
+        }
         report_eod_matches(id, scratch, onEvent, context);
     }
 
diff --git a/unit/hyperscan/arg_checks.cpp b/unit/hyperscan/arg_checks.cpp
index f717f0dc..dbc692c5 100644
--- a/unit/hyperscan/arg_checks.cpp
+++ b/unit/hyperscan/arg_checks.cpp
@@ -740,7 +740,9 @@ TEST(HyperscanArgChecks, ResetAndCopyStreamSameToId) {
     hs_free_database(db);
 }
 
-TEST(HyperscanArgChecks, ResetAndCopyStreamNoScratch) {
+// hs_reset_and_copy_stream: You're allowed to reset and copy a stream with no
+// scratch and no callback.
+TEST(HyperscanArgChecks, ResetAndCopyStreamNoCallbackOrScratch) {
     hs_stream_t *stream = nullptr;
     hs_stream_t *stream_to = nullptr;
     hs_database_t *db = nullptr;
@@ -760,6 +762,37 @@ TEST(HyperscanArgChecks, ResetAndCopyStreamNoScratch) {
     ASSERT_EQ(HS_SUCCESS, err);
 
     err = hs_reset_and_copy_stream(stream_to, stream, nullptr, nullptr, nullptr);
+    ASSERT_EQ(HS_SUCCESS, err);
+
+    hs_close_stream(stream_to, scratch, nullptr, nullptr);
+    hs_close_stream(stream, scratch, nullptr, nullptr);
+    hs_free_scratch(scratch);
+    hs_free_database(db);
+}
+
+// hs_reset_and_copy_stream: If you specify a callback, you must provide
+// scratch.
+TEST(HyperscanArgChecks, ResetAndCopyStreamNoScratch) {
+    hs_stream_t *stream = nullptr;
+    hs_stream_t *stream_to = nullptr;
+    hs_database_t *db = nullptr;
+    hs_compile_error_t *compile_err = nullptr;
+    hs_error_t err = hs_compile("foobar", 0, HS_MODE_STREAM, nullptr, &db,
+                                &compile_err);
+    ASSERT_EQ(HS_SUCCESS, err);
+
+    hs_scratch_t *scratch = nullptr;
+    err = hs_alloc_scratch(db, &scratch);
+    ASSERT_EQ(HS_SUCCESS, err);
+
+    err = hs_open_stream(db, 0, &stream);
+    ASSERT_EQ(HS_SUCCESS, err);
+
+    err = hs_open_stream(db, 0, &stream_to);
+    ASSERT_EQ(HS_SUCCESS, err);
+
+    err = hs_reset_and_copy_stream(stream_to, stream, nullptr, dummy_cb,
+                                   nullptr);
     ASSERT_EQ(HS_INVALID, err);
 
     hs_close_stream(stream_to, scratch, nullptr, nullptr);
@@ -793,7 +826,8 @@ TEST(HyperscanArgChecks, ResetAndCopyStreamDiffDb) {
     err = hs_open_stream(db2, 0, &stream_to);
     ASSERT_EQ(HS_SUCCESS, err);
 
-    err = hs_reset_and_copy_stream(stream_to, stream, scratch, nullptr, nullptr);
+    err = hs_reset_and_copy_stream(stream_to, stream, scratch, nullptr,
+                                   nullptr);
     ASSERT_EQ(HS_INVALID, err);
 
     hs_close_stream(stream_to, scratch, nullptr, nullptr);
@@ -2009,6 +2043,7 @@ TEST(HyperscanArgChecks, ScanStreamBadScratch) {
     free(local_garbage);
 }
 
+// hs_reset_stream: bad scratch arg
 TEST(HyperscanArgChecks, ResetStreamBadScratch) {
     hs_database_t *db = nullptr;
     hs_compile_error_t *compile_err = nullptr;
@@ -2025,7 +2060,7 @@ TEST(HyperscanArgChecks, ResetStreamBadScratch) {
     ASSERT_EQ(HS_SUCCESS, err);
     ASSERT_TRUE(stream != nullptr);
 
-    err = hs_reset_stream(stream, 0, scratch, nullptr, nullptr);
+    err = hs_reset_stream(stream, 0, scratch, dummy_cb, nullptr);
     EXPECT_NE(HS_SUCCESS, err);
     EXPECT_NE(HS_SCAN_TERMINATED, err);
 
diff --git a/unit/hyperscan/stream_op.cpp b/unit/hyperscan/stream_op.cpp
index fbec6b98..a78e08a1 100644
--- a/unit/hyperscan/stream_op.cpp
+++ b/unit/hyperscan/stream_op.cpp
@@ -69,7 +69,9 @@ TEST(StreamUtil, reset1) {
 
     c.matches.clear();
 
-    err = hs_reset_stream(stream, 0, scratch, nullptr, nullptr);
+    // Note: we do not need matches from this reset operation, so we do not
+    // need to supply a callback or scratch space.
+    err = hs_reset_stream(stream, 0, nullptr, nullptr, nullptr);
     ASSERT_EQ(HS_SUCCESS, err);
 
     err = hs_scan_stream(stream, data1, sizeof(data1), 0, scratch, record_cb2,
@@ -107,7 +109,9 @@ TEST(StreamUtil, reset2) {
 
     c.matches.clear();
 
-    err = hs_reset_stream(stream, 0, scratch, nullptr, nullptr);
+    // Note: we do not need matches from this reset operation, so we do not
+    // need to supply a callback or scratch space.
+    err = hs_reset_stream(stream, 0, nullptr, nullptr, nullptr);
     ASSERT_EQ(HS_SUCCESS, err);
 
     err = hs_scan_stream(stream, data1, sizeof(data1), 0, scratch, record_cb,
@@ -268,7 +272,7 @@ TEST(StreamUtil, copy_reset1) {
 
     c.matches.clear();
 
-    err = hs_reset_and_copy_stream(stream, stream2, scratch, nullptr, nullptr);
+    err = hs_reset_and_copy_stream(stream, stream2, nullptr, nullptr, nullptr);
     ASSERT_EQ(HS_SUCCESS, err);
 
     err = hs_scan_stream(stream, data1, sizeof(data1), 0, scratch, record_cb2,
@@ -312,7 +316,7 @@ TEST(StreamUtil, copy_reset2) {
 
     c.matches.clear();
 
-    err = hs_reset_and_copy_stream(stream, stream2, scratch, nullptr, nullptr);
+    err = hs_reset_and_copy_stream(stream, stream2, nullptr, nullptr, nullptr);
     ASSERT_EQ(HS_SUCCESS, err);
 
     err = hs_scan_stream(stream, data1, sizeof(data1), 0, scratch, record_cb,
@@ -355,7 +359,7 @@ TEST(StreamUtil, copy_reset3) {
 
     c.matches.clear();
 
-    err = hs_reset_and_copy_stream(stream2, stream, scratch, nullptr, nullptr);
+    err = hs_reset_and_copy_stream(stream2, stream, nullptr, nullptr, nullptr);
     ASSERT_EQ(HS_SUCCESS, err);
 
     err = hs_scan_stream(stream, data1, sizeof(data1), 0, scratch, record_cb,
@@ -408,7 +412,7 @@ TEST(StreamUtil, copy_reset4) {
 
     c.matches.clear();
 
-    err = hs_reset_and_copy_stream(stream2, stream, scratch, nullptr, nullptr);
+    err = hs_reset_and_copy_stream(stream2, stream, nullptr, nullptr, nullptr);
     ASSERT_EQ(HS_SUCCESS, err);
 
     err = hs_scan_stream(stream, data1, sizeof(data1), 0, scratch, record_cb,
@@ -458,7 +462,7 @@ TEST(StreamUtil, copy_reset5) {
     ASSERT_EQ(HS_SUCCESS, err);
     ASSERT_EQ(0U, c.matches.size());
 
-    err = hs_reset_and_copy_stream(stream2, stream, scratch, nullptr, nullptr);
+    err = hs_reset_and_copy_stream(stream2, stream, nullptr, nullptr, nullptr);
     ASSERT_EQ(HS_SUCCESS, err);
 
     err = hs_scan_stream(stream, data1, sizeof(data1), 0, scratch, record_cb,