diff --git a/include/asm/output.h b/include/asm/output.h
index 03ef4d09..e3dde6a5 100644
--- a/include/asm/output.h
+++ b/include/asm/output.h
@@ -19,7 +19,7 @@ extern char *tzObjectname;
 extern struct Section *pSectionList, *pCurrentSection;
 
 void out_SetFileName(char *s);
-void out_CreatePatch(uint32_t type, struct Expression *expr);
+void out_CreatePatch(uint32_t type, struct Expression const *expr);
 void out_WriteObject(void);
 
 #endif /* RGBDS_ASM_OUTPUT_H */
diff --git a/include/asm/rpn.h b/include/asm/rpn.h
index 38de7fc1..7d8f6d74 100644
--- a/include/asm/rpn.h
+++ b/include/asm/rpn.h
@@ -25,8 +25,6 @@ struct Expression {
 	uint32_t nRPNCapacity;  // Size of the `tRPN` buffer
 	uint32_t nRPNLength;    // Used size of the `tRPN` buffer
 	uint32_t nRPNPatchSize; // Size the expression will take in the obj file
-	// FIXME: does this need to be part of the struct?
-	uint32_t nRPNOut;       // How many bytes have been written
 };
 
 /* FIXME: Should be defined in `asmy.h`, but impossible with POSIX Yacc */
@@ -44,7 +42,6 @@ void rpn_HIGH(struct Expression *expr, const struct Expression *src);
 void rpn_LOW(struct Expression *expr, const struct Expression *src);
 void rpn_UNNEG(struct Expression *expr, const struct Expression *src);
 void rpn_UNNOT(struct Expression *expr, const struct Expression *src);
-uint16_t rpn_PopByte(struct Expression *expr);
 void rpn_BankSymbol(struct Expression *expr, char *tzSym);
 void rpn_BankSection(struct Expression *expr, char *tzSectionName);
 void rpn_BankSelf(struct Expression *expr);
diff --git a/src/asm/output.c b/src/asm/output.c
index 6bc65af3..b2913ca9 100644
--- a/src/asm/output.c
+++ b/src/asm/output.c
@@ -310,10 +310,9 @@ struct Patch *allocpatch(void)
 /*
  * Create a new patch (includes the rpn expr)
  */
-void out_CreatePatch(uint32_t type, struct Expression *expr)
+void out_CreatePatch(uint32_t type, struct Expression const *expr)
 {
 	struct Patch *pPatch;
-	uint16_t rpndata;
 	uint8_t *rpnexpr;
 	char tzSym[512];
 	uint32_t rpnptr = 0, symptr;
@@ -328,19 +327,22 @@ void out_CreatePatch(uint32_t type, struct Expression *expr)
 	fstk_DumpToStr(pPatch->tzFilename, sizeof(pPatch->tzFilename));
 	pPatch->nOffset = pCurrentSection->nPC;
 
-	while ((rpndata = rpn_PopByte(expr)) != 0xDEAD) {
+	for (size_t offset = 0; offset < expr->nRPNLength; ) {
+#define popbyte(expr) (expr)->tRPN[offset++]
+		uint8_t rpndata = popbyte(expr);
+
 		switch (rpndata) {
 		case RPN_CONST:
 			rpnexpr[rpnptr++] = RPN_CONST;
-			rpnexpr[rpnptr++] = rpn_PopByte(expr);
-			rpnexpr[rpnptr++] = rpn_PopByte(expr);
-			rpnexpr[rpnptr++] = rpn_PopByte(expr);
-			rpnexpr[rpnptr++] = rpn_PopByte(expr);
+			rpnexpr[rpnptr++] = popbyte(expr);
+			rpnexpr[rpnptr++] = popbyte(expr);
+			rpnexpr[rpnptr++] = popbyte(expr);
+			rpnexpr[rpnptr++] = popbyte(expr);
 			break;
 		case RPN_SYM:
 		{
 			symptr = 0;
-			while ((tzSym[symptr++] = rpn_PopByte(expr)) != 0)
+			while ((tzSym[symptr++] = popbyte(expr)) != 0)
 				;
 
 			struct sSymbol const *sym = sym_FindSymbol(tzSym);
@@ -371,7 +373,7 @@ void out_CreatePatch(uint32_t type, struct Expression *expr)
 			struct sSymbol *sym;
 
 			symptr = 0;
-			while ((tzSym[symptr++] = rpn_PopByte(expr)) != 0)
+			while ((tzSym[symptr++] = popbyte(expr)) != 0)
 				;
 
 			sym = sym_FindSymbol(tzSym);
@@ -393,7 +395,7 @@ void out_CreatePatch(uint32_t type, struct Expression *expr)
 			rpnexpr[rpnptr++] = RPN_BANK_SECT;
 
 			do {
-				b = rpn_PopByte(expr);
+				b = popbyte(expr);
 				rpnexpr[rpnptr++] = b & 0xFF;
 			} while (b != 0);
 			break;
@@ -402,6 +404,7 @@ void out_CreatePatch(uint32_t type, struct Expression *expr)
 			rpnexpr[rpnptr++] = rpndata;
 			break;
 		}
+#undef popbyte
 	}
 
 	assert(rpnptr == expr->nRPNPatchSize);
diff --git a/src/asm/rpn.c b/src/asm/rpn.c
index 059e2def..d3bf665a 100644
--- a/src/asm/rpn.c
+++ b/src/asm/rpn.c
@@ -81,7 +81,6 @@ void rpn_Init(struct Expression *expr)
 	expr->nRPNCapacity = 0;
 	expr->nRPNLength = 0;
 	expr->nRPNPatchSize = 0;
-	expr->nRPNOut = 0;
 }
 
 /*
@@ -94,17 +93,6 @@ void rpn_Free(struct Expression *expr)
 	rpn_Init(expr);
 }
 
-/*
- * Returns the next rpn byte in expression
- */
-uint16_t rpn_PopByte(struct Expression *expr)
-{
-	if (expr->nRPNOut == expr->nRPNLength)
-		return 0xDEAD;
-
-	return expr->tRPN[expr->nRPNOut++];
-}
-
 /*
  * Determine if the current expression is known at assembly time
  */