diff --git a/include/liquid.h b/include/liquid.h
index f5f2ab0ae..bbb18914f 100644
--- a/include/liquid.h
+++ b/include/liquid.h
@@ -4962,6 +4962,10 @@ int SYMSYNC(_lock)(SYMSYNC() _q);                                           \
 /* Unlock the symbol synchronizer's loop control                        */  \
 int SYMSYNC(_unlock)(SYMSYNC() _q);                                         \
                                                                             \
+/* Check the lock state of the symbol synchronizer's loop control,      */  \
+/* returning 1 if the object is locked, 0 if unlocked.                  */  \
+int SYMSYNC(_is_locked)(SYMSYNC() _q);                                      \
+                                                                            \
 /* Set synchronizer output rate (samples/symbol)                        */  \
 /*  _q      : synchronizer object                                       */  \
 /*  _k_out  : output samples/symbol, _k_out > 0                         */  \
diff --git a/src/filter/src/symsync.proto.c b/src/filter/src/symsync.proto.c
index 0702772f5..4a7a43bb6 100644
--- a/src/filter/src/symsync.proto.c
+++ b/src/filter/src/symsync.proto.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2007 - 2022 Joseph Gaeddert
+ * Copyright (c) 2007 - 2024 Joseph Gaeddert
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -377,6 +377,12 @@ int SYMSYNC(_unlock)(SYMSYNC() _q)
     return LIQUID_OK;
 }
 
+// check lock state
+int SYMSYNC(_is_locked)(SYMSYNC() _q)
+{
+    return _q->is_locked;
+}
+
 // set synchronizer output rate (samples/symbol)
 //  _q      :   synchronizer object
 //  _k_out  :   output samples/symbol
diff --git a/src/filter/tests/symsync_copy_autotest.c b/src/filter/tests/symsync_copy_autotest.c
index 5541d770a..4c304b733 100644
--- a/src/filter/tests/symsync_copy_autotest.c
+++ b/src/filter/tests/symsync_copy_autotest.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2007 - 2022 Joseph Gaeddert
+ * Copyright (c) 2007 - 2024 Joseph Gaeddert
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -85,15 +85,28 @@ void autotest_symsync_config()
     CONTEND_ISNULL( symsync_crcf_create(2, 12, NULL,  0) ); // h_len is too small
     CONTEND_ISNULL( symsync_crcf_create(2, 12, NULL, 47) ); // h_len is not divisible by M
 
+    CONTEND_ISNULL( symsync_crcf_create_kaiser(0, 12, 0.2, 48) ); // k is too small
+    CONTEND_ISNULL( symsync_crcf_create_kaiser(2,  0, 0.2, 48) ); // m is too small
+    CONTEND_ISNULL( symsync_crcf_create_kaiser(2, 12, 7.2, 48) ); // beta is too large
+    CONTEND_ISNULL( symsync_crcf_create_kaiser(2, 12, 0.2,  0) ); // M is too small
+
     //CONTEND_ISNULL( symsync_crcf_create_nyquist(2, 12, NULL, 47) ); // h_len is not divisible by M
 
-    // // create valid object
-    // symsync_crcf q = symsync_crcf_create ...
-    // CONTEND_EQUALITY( LIQUID_OK, symsync_crcf_print(filter) );
+    // create valid object
+    symsync_crcf q = symsync_crcf_create_kaiser(2, 12, 0.2, 48);
+    CONTEND_EQUALITY( LIQUID_OK, symsync_crcf_print(q) );
+
+    // check lock state
+    CONTEND_EQUALITY( symsync_crcf_lock(q), LIQUID_OK );
+    CONTEND_TRUE    ( symsync_crcf_is_locked(q) );
+    CONTEND_EQUALITY( symsync_crcf_unlock(q), LIQUID_OK );
+    CONTEND_FALSE   ( symsync_crcf_is_locked(q) );
 
-    // // check properties ...
+    // check invalid properties
+    CONTEND_EQUALITY( LIQUID_EICONFIG, symsync_crcf_set_output_rate(q, 0) );
+    CONTEND_EQUALITY( LIQUID_EICONFIG, symsync_crcf_set_lf_bw(q, -1) );
 
-    // // destroy object
-    // symsync_crcf_destroy(filter);
+    // destroy object
+    symsync_crcf_destroy(q);
 }