diff --git a/asminc/telestrat.inc b/asminc/telestrat.inc
index df607e375..956f4b8ac 100644
--- a/asminc/telestrat.inc
+++ b/asminc/telestrat.inc
@@ -195,6 +195,7 @@ XDECAL           = $18
 
 XTEXT            = $19
 XHIRES           = $1A
+XEFFHI           = $1B          ; Clear hires screen
 XFILLM           = $1C
 XMINMA           = $1F
 XVARS            = $24          ; Only in TELEMON 3.x, in TELEMON 2.4, it's XNOMFI ($24)
diff --git a/libsrc/telestrat/tgi/telestrat-228-200-3.s b/libsrc/telestrat/tgi/telestrat-228-200-3.s
index ce501f0bf..228bdce99 100644
--- a/libsrc/telestrat/tgi/telestrat-228-200-3.s
+++ b/libsrc/telestrat/tgi/telestrat-228-200-3.s
@@ -170,7 +170,7 @@ CONTROL:
 ;
 
 CLEAR:
-        ; not done yet
+        BRK_TELEMON(XEFFHI)
         rts
 
 ; ------------------------------------------------------------------------
diff --git a/libsrc/telestrat/tgi/telestrat-240-200-2.s b/libsrc/telestrat/tgi/telestrat-240-200-2.s
index 3ee918c4f..9bffebb0c 100644
--- a/libsrc/telestrat/tgi/telestrat-240-200-2.s
+++ b/libsrc/telestrat/tgi/telestrat-240-200-2.s
@@ -169,7 +169,7 @@ CONTROL:
 ;
 
 CLEAR:
-        ; not done yet
+        BRK_TELEMON(XEFFHI)
         rts
 
 ; ------------------------------------------------------------------------