diff --git a/Programs/CosmOS/Assembler/source.asm b/Programs/CosmOS/Assembler/source.asm
index 89eed7a..a24f470 100644
--- a/Programs/CosmOS/Assembler/source.asm
+++ b/Programs/CosmOS/Assembler/source.asm
@@ -249,11 +249,29 @@ srcNext:
   LDA.0
   BNA srcAtEnd
 
-  ; Is the buffer used up? SrcAt counts how far into it we have read and SrcCount how many
-  ; of its bytes are the file's, which is 256 for every block but a short last one.
+  ; ---- Is the buffer used up? ----
+  ;
+  ; SrcAt counts how far into it we have read and SrcCount how many of its bytes are the
+  ; file's, which is 256 for every block but a short last one.
+  ;
+  ; ASKED HERE RATHER THAN BY numCompare, because this is the hottest question in the
+  ; assembler - every character of every pass asks it - and a call to answer it costs more
+  ; than the answer. The high bytes settle it almost every time and settle it FIRST: a full
+  ; block is 256, so SrcCount's high byte is one and SrcAt's is nought until the last
+  ; sixteenth of the block. Six instructions, where the call was twenty.
   SETD.0 SrcAt
   SETD.2 SrcCount
-  CALL numCompare
+  LDA.0
+  LDB.2
+  CCF
+  SUB
+  BNQ srcHaveByte
+  INCD.0
+  INCD.2
+  LDA.0
+  LDB.2
+  CCF
+  SUB
   BNQ srcHaveByte
   CALL srcLoad
   BNQ srcAtEnd
@@ -266,19 +284,31 @@ srcHaveByte:
   STD.0.1
   SETD.0 SrcChar
   STA.0
-  SETD.0 SrcAt
-  CALL numStep
 
-  ; A newline is what makes the next character part of the next line. Counting it here,
-  ; as it is handed out, means the line number always describes the character just given.
-  SETD.0 SrcChar
-  LDA.0
+  ; ---- A newline is what makes the next character part of the next line ----
+  ;
+  ; Counted here, as the character is handed out, so the line number always describes the
+  ; character just given. A still holds it - nothing since the load has wanted it - where
+  ; this used to fetch it back out of SrcChar it had just been put in.
   INIB 0x0A
   XOR
-  BNQ srcNextDone
+  BNQ srcNextStep
   SETD.0 SrcLine
   CALL numStep
 
+srcNextStep:
+  ; And one further into the buffer, counted the same way and for the same reason.
+  SETD.0 SrcAt
+  INCD.0
+  LDA.0
+  INCA
+  STA.0
+  BNC srcNextDone
+  DECD.0
+  LDA.0
+  INCA
+  STA.0
+
 srcNextDone:
   RSTA
   RSTB