diff --git a/apps/zasm/const.asm b/apps/zasm/const.asm
index 2f9db4e..dfddfd6 100644
--- a/apps/zasm/const.asm
+++ b/apps/zasm/const.asm
@@ -13,3 +13,9 @@
 .equ	ERR_OVFL		0x04
 
 .equ	ERR_FILENOTFOUND	0x05
+
+; Duplicate symbol
+.equ	ERR_DUPSYM		0x06
+
+; Out of memory
+.equ	ERR_OOM			0x07
diff --git a/apps/zasm/directive.asm b/apps/zasm/directive.asm
index 99d7b88..181490d 100644
--- a/apps/zasm/directive.asm
+++ b/apps/zasm/directive.asm
@@ -104,6 +104,8 @@ handleDW:
 	ret
 
 handleEQU:
+	call	zasmIsLocalPass	; Are we in local pass? Then ignore all .equ.
+	jr	z, .skip		; they mess up duplicate symbol detection.
 	push	hl
 	push	de
 	push	bc
@@ -124,8 +126,7 @@ handleEQU:
 	jr	nz, .badarg
 	ld	hl, DIREC_SCRATCHPAD
 	push	ix \ pop de
-	call	symRegister	; TODO: handle duplicate symbol error, OOM, etc.
-	cp	a		; ensure Z
+	call	symRegister	; A and Z set
 	jr	.end
 .badfmt:
 	ld	a, ERR_BAD_FMT
@@ -139,6 +140,10 @@ handleEQU:
 	pop	de
 	pop	hl
 	ret
+.skip:
+	; consume args and return
+	call	readWord
+	jp	readWord
 
 handleORG:
 	call	readWord
diff --git a/apps/zasm/main.asm b/apps/zasm/main.asm
index 4b3f1aa..34684be 100644
--- a/apps/zasm/main.asm
+++ b/apps/zasm/main.asm
@@ -120,8 +120,7 @@ _parseInstr:
 
 _parseDirec:
 	ld	a, c		; D_*
-	call	parseDirective
-	ret
+	jp	parseDirective
 
 _parseLabel:
 	; The string in (scratchpad) is a label with its trailing ':' removed.
diff --git a/apps/zasm/symbol.asm b/apps/zasm/symbol.asm
index 2b09336..69e483a 100644
--- a/apps/zasm/symbol.asm
+++ b/apps/zasm/symbol.asm
@@ -11,11 +11,6 @@
 ; and continue second pass as usual.
 
 ; *** Constants ***
-; Duplicate symbol in registry
-.equ	SYM_ERR_DUPLICATE	0x01
-; Symbol registry buffer is full
-.equ	SYM_ERR_FULLBUF		0x02
-
 ; Maximum number of symbols we can have in the global registry
 .equ	SYM_MAXCOUNT		0x200
 ; Maximum number of symbols we can have in the local registry
@@ -153,7 +148,7 @@ symNamesEnd:
 ; Register label in (HL) (minus the ending ":") into the symbol registry and
 ; set its value in that registry to DE.
 ; If successful, Z is set and A is the symbol index. Otherwise, Z is unset and
-; A is an error code (SYM_ERR_*).
+; A is an error code (ERR_*).
 symRegister:
 	call	symFind
 	jr	z, .alreadyThere
@@ -167,7 +162,7 @@ symRegister:
 	ld	c, a		; save that strlen for later
 
 	call	symNamesEnd
-	jr	nz, .error
+	jr	nz, .outOfMemory
 
 	; Is our new name going to make us go out of bounds?
 	push	hl
@@ -178,7 +173,7 @@ symRegister:
 		call	cpHLDE
 	pop	de
 	pop	hl
-	jr	nc, .error	; HL >= DE
+	jr	nc, .outOfMemory	; HL >= DE
 
 	; Success. At this point, we have:
 	; HL -> where we want to add the string
@@ -201,16 +196,37 @@ symRegister:
 	; list. DE is already correctly placed, A is already zero
 	ld	(de), a
 
+	cp	a		; ensure Z
 	; Nothing to pop. We've already popped our stack in the lines above.
 	ret
 
-.error:
+.outOfMemory:
+	ld	a, ERR_OOM
 	call	unsetZ
 	pop	de
 	pop	hl
 	ret
 
 .alreadyThere:
+	; We are in a tricky situation with regards to our handling of the
+	; duplicate symbol error. Normally, it should be straightforward: We
+	; only register labels during first pass and evaluate constants during
+	; the second. Easy.
+	; We can *almost* do that... but we have ".org". .org affects label
+	; values and supports expressions, which means that we have to evaluate
+	; constants during first pass. But because we can possibly have forward
+	; references in ".equ", some constants are going to have a bad value.
+	; Therefore, we really can't evaluate all constants during the first
+	; pass.
+	; With this situation, how do you manage detection of duplicate symbols?
+	; By limiting the "duplicate error" condition to the first pass. During,
+	; first pass, sure, we don't have our proper values, but we have all our
+	; symbol names. So, if we end up in .alreadyThere during first pass,
+	; then it's an error condition. If it's not first pass, then we need
+	; to update our value.
+	call	zasmIsFirstPass
+	jr	z, .duplicateError
+	; Second pass. Don't error out, just update value
 	push	hl
 	ld	hl, (SYM_CTX_PTR)
 	ex	de, hl
@@ -218,6 +234,9 @@ symRegister:
 	pop	hl
 	cp	a		; ensure Z
 	ret
+.duplicateError:
+	ld	a, ERR_DUPSYM
+	jp	unsetZ		; return
 
 ; Select global or local registry according to label name in (HL)
 symSelect:
@@ -246,7 +265,6 @@ symFind:
 	inc	ix
 	inc	ix
 	jr	.loop
-	; exhausted djnz? no match
 .nomatch:
 	call	unsetZ
 	jr	.end
diff --git a/tools/tests/unit/test_expr.asm b/tools/tests/unit/test_expr.asm
index eec8984..fd6b0f3 100644
--- a/tools/tests/unit/test_expr.asm
+++ b/tools/tests/unit/test_expr.asm
@@ -4,6 +4,7 @@ jp	test
 #include "core.asm"
 #include "parse.asm"
 #include "zasm/util.asm"
+#include "zasm/const.asm"
 #include "zasm/parse.asm"
 .equ	SYM_RAMSTART	RAMSTART
 #include "zasm/symbol.asm"
diff --git a/tools/tests/unit/test_symbol.asm b/tools/tests/unit/test_symbol.asm
index a2aefdb..03bd791 100644
--- a/tools/tests/unit/test_symbol.asm
+++ b/tools/tests/unit/test_symbol.asm
@@ -3,9 +3,14 @@ jp	test
 
 #include "core.asm"
 #include "zasm/util.asm"
+#include "zasm/const.asm"
 .equ	SYM_RAMSTART	RAMSTART
 #include "zasm/symbol.asm"
 
+; Pretend that we aren't in first pass
+zasmIsFirstPass:
+	jp	unsetZ
+
 testNum:	.db 1
 
 sFOO:		.db "FOO", 0
diff --git a/tools/tests/zasm/errtests.sh b/tools/tests/zasm/errtests.sh
index b48d8cf..834f8a0 100755
--- a/tools/tests/zasm/errtests.sh
+++ b/tools/tests/zasm/errtests.sh
@@ -16,6 +16,24 @@ chkerr() {
     fi
 }
 
+chkoom() {
+    echo "Trying OOM error..."
+    local s=""
+    # 300 x 27-29 bytes > 8192 bytes. Large enough to smash the pool.
+    for i in {1..300}; do
+        s+=".equ abcdefghijklmnopqrstuvwxyz$i 42"
+        s+=$'\n'
+    done
+    ${ZASM} <<< "$s" > /dev/null
+    local res=$?
+    if [[ $res == 7 ]]; then
+        echo "Good!"
+    else
+        echo "$res != 7"
+        exit 1
+    fi
+}
+
 chkerr "foo" 1
 chkerr "ld a, foo" 2
 chkerr "ld a, hl" 2
@@ -37,3 +55,5 @@ chkerr "#inc foo" 3
 chkerr "ld a, 0x100" 4
 chkerr ".db 0x100" 4
 chkerr "#inc \"doesnotexist\"" 5
+chkerr ".equ foo 42 \\ .equ foo 42" 6
+chkoom