diff --git a/src/a1cmd.pla b/src/a1cmd.pla
index bced974..2e4b2b5 100644
--- a/src/a1cmd.pla
+++ b/src/a1cmd.pla
@@ -85,7 +85,7 @@ byte hexchar[]    = '0','1','2','3','4','5','6','7','8','9','A','B','C','D','E',
 word systemflags = 0
 word heap
 word symtbl, lastsym
-word perr
+byte perr, lerr
 word cmdptr
 ;
 ; CALL SOS
@@ -670,19 +670,23 @@ def addmod(mod, addr)
     return addtbl(modtosym(mod, @dci), addr, @lastsym)
 end
 def lookupextern(esd, index)
-    word sym
+    word sym, addr
     byte str[16]
     while ^esd
         sym = esd
         esd = esd + dcitos(esd, @str)
         if (esd).0 & $10 and (esd).1 == index
-            return lookupsym(sym)
+            addr = lookupsym(sym)
+	    if !addr
+                lerr = $81
+	        cout('?')
+		prstr(@str)
+		crout
+	    fin
+            return addr
         fin
         esd = esd + 3
     loop
-    prbyte(index)
-    cout('?')
-    crout
     return 0
 end
 def adddef(addr, deflast)
@@ -710,6 +714,7 @@ def loadmod(mod)
     word deftbl, deflast
     word moddep, rld, esd, sym
     byte str[17], filename[17]
+    lerr = 0
     ;
     ; Read the RELocatable module header (first 128 bytes)
     ;
@@ -841,6 +846,9 @@ def loadmod(mod)
         perr = perr | 0x100
         return -perr
     fin
+    if lerr
+        return -lerr
+    fin
     ;
     ; Call init routine if it exists.
     ;
diff --git a/src/cmd.pla b/src/cmd.pla
index da9e3f6..2d14a91 100644
--- a/src/cmd.pla
+++ b/src/cmd.pla
@@ -87,7 +87,7 @@ word heap
 word lastsym     = symtbl
 word xheap       = $0800
 word systemflags = 0
-word perr
+byte perr, lerr
 word cmdptr
 ;
 ; Utility functions
@@ -925,13 +925,20 @@ def addmod(mod, addr)
     return addtbl(modtosym(mod, @dci), addr, @lastsym)
 end
 def lookupextern(esd, index)
-    word sym
+    word sym, addr
     byte str[16]
     while ^esd
         sym = esd
         esd = esd + dcitos(esd, @str)
         if (esd).0 & $10 and (esd).1 == index
-            return lookupsym(sym)
+            addr = lookupsym(sym)
+	    if !addr
+                lerr = $81
+	        cout('?')
+		prstr(@str)
+		crout
+	    fin
+            return addr
         fin
         esd = esd + 3
     loop
@@ -967,6 +974,7 @@ def loadmod(mod)
     word moddep, rld, esd, sym
     byte defbank, str[16], filename[64]
     byte header[128]
+    lerr = 0
     ;
     ; Read the RELocatable module header (first 128 bytes)
     ;
@@ -1127,6 +1135,9 @@ def loadmod(mod)
         perr = perr | 0x100
         return -perr
     fin
+    if lerr
+        return -lerr
+    fin
     ;
     ; Call init routine if it exists.
     ;
diff --git a/src/soscmd.pla b/src/soscmd.pla
index 63e8a13..3612467 100644
--- a/src/soscmd.pla
+++ b/src/soscmd.pla
@@ -89,7 +89,7 @@ byte modseg[15]
 word heap        = $2000
 word symtbl, lastsym
 word refcons, devcons
-word perr, terr
+byte perr, terr, lerr
 word cmdptr
 ;
 ; CALL SOS
@@ -890,19 +890,23 @@ def addmod(mod, addr)
     return addtbl(modtosym(mod, @dci), addr, @lastsym)
 end
 def lookupextern(esd, index)
-    word sym
+    word sym, addr
     byte str[16]
     while ^esd
         sym = esd
         esd = esd + dcitos(esd, @str)
         if (esd).0 & $10 and (esd).1 == index
-            return lookupsym(sym)
+            addr = lookupsym(sym)
+	    if !addr
+                lerr = $81
+	        cout('?')
+		prstr(@str)
+		crout
+	    fin
+            return addr
         fin
         esd = esd + 3
     loop
-    prbyte(index)
-    cout('?')
-    crout
     return 0
 end
 def adddef(ext, addr, deflast)
@@ -944,6 +948,7 @@ def loadmod(mod)
     word moddep, rld, esd, sym
     byte defext, str[16], filename[33]
     byte header[128]
+    lerr = 0
     ;
     ; Read the RELocatable module header (first 128 bytes)
     ;
@@ -1148,6 +1153,9 @@ def loadmod(mod)
         perr = perr | 0x100
         return -perr
     fin
+    if lerr
+        return -lerr
+    fin
     ;
     ; Call init routine if it exists.
     ;