diff --git a/phsource/ph_bulgarian b/phsource/ph_bulgarian
index 005c03f7..832f8851 100644
--- a/phsource/ph_bulgarian
+++ b/phsource/ph_bulgarian
@@ -81,8 +81,8 @@ phoneme r
 endphoneme
 
 phoneme x
-  voicingswitch x   // [x] doesn't switch to [Q]
   import_phoneme base/x
+  voicingswitch x   // [x] doesn't switch to [Q]
 endphoneme
 
 
diff --git a/phsource/ph_burmese b/phsource/ph_burmese
index a706cbce..599d9f57 100644
--- a/phsource/ph_burmese
+++ b/phsource/ph_burmese
@@ -470,7 +470,7 @@ phoneme b
 endphoneme
 
 phoneme ph //aspirated
-  vls blb stop
+  //vls blb stop
   import_phoneme base/p
 endphoneme
 
@@ -485,7 +485,7 @@ phoneme d
 endphoneme
 
 phoneme th
-  vls alv stop
+  //vls alv stop
   import_phoneme base/t
 endphoneme
 
@@ -515,7 +515,7 @@ phoneme g
 endphoneme
 
 phoneme kh
-  vls vel stop
+  //vls vel stop
   import_phoneme base/k
 endphoneme
 
diff --git a/phsource/ph_kyrgyz b/phsource/ph_kyrgyz
index c443ce1b..15eff26a 100644
--- a/phsource/ph_kyrgyz
+++ b/phsource/ph_kyrgyz
@@ -448,7 +448,6 @@ endphoneme
 
 phoneme ts
   ipa ts        
-  Length 10
   import_phoneme consonants/ts
 endphoneme
 
diff --git a/phsource/ph_lithuanian b/phsource/ph_lithuanian
index 117c9c3d..8711f404 100644
--- a/phsource/ph_lithuanian
+++ b/phsource/ph_lithuanian
@@ -228,7 +228,6 @@ endphoneme
 
 
 phoneme ts
-  Length 10
   import_phoneme consonants/ts
 endphoneme
 
diff --git a/phsource/ph_russian b/phsource/ph_russian
index fe90ec27..78a7d519 100644
--- a/phsource/ph_russian
+++ b/phsource/ph_russian
@@ -148,7 +148,6 @@ endphoneme
 
 
 phoneme ts
-  Length 10
   import_phoneme consonants/ts
 endphoneme
 
diff --git a/src/libespeak-ng/compiledata.c b/src/libespeak-ng/compiledata.c
index 8bcdbfd9..b54859bf 100644
--- a/src/libespeak-ng/compiledata.c
+++ b/src/libespeak-ng/compiledata.c
@@ -1907,6 +1907,15 @@ static void ImportPhoneme(void)
 		return;
 	}
 
+	if (phoneme_out->phflags != 0 ||
+	    phoneme_out->type != phINVALID ||
+	    phoneme_out->start_type != 0 ||
+	    phoneme_out->end_type != 0 ||
+	    phoneme_out->std_length != 0 ||
+	    phoneme_out->length_mod != 0) {
+		error("Phoneme import will override set properties.");
+	}
+
 	ph_mnem = phoneme_out->mnemonic;
 	ph_code = phoneme_out->code;
 	memcpy(phoneme_out, ph, sizeof(PHONEME_TAB));