diff --git a/src/devices/cpu/z8/z8.cpp b/src/devices/cpu/z8/z8.cpp
index 3545b7cf620..9b2febe17fc 100644
--- a/src/devices/cpu/z8/z8.cpp
+++ b/src/devices/cpu/z8/z8.cpp
@@ -12,7 +12,6 @@
 
     - strobed I/O
     - expose register file to disassembler
-    - decimal adjust instruction
     - timer Tin/Tout modes
     - serial
     - instruction pipeline
diff --git a/src/devices/cpu/z8/z8ops.hxx b/src/devices/cpu/z8/z8ops.hxx
index fbab7c3385c..2e42640a344 100644
--- a/src/devices/cpu/z8/z8ops.hxx
+++ b/src/devices/cpu/z8/z8ops.hxx
@@ -308,6 +308,25 @@ INSTRUCTION( cp_IR1_IM )        { mode_IR1_IM(compare) }
 
 void z8_device::decimal_adjust(uint8_t dst)
 {
+	uint8_t data = register_read(dst);
+	uint16_t new_data = data;
+	if (flag(D))
+	{
+		if (flag(H) | ((data&0xf)>9)) new_data-=6;
+		if (flag(C) | (data>0x99)) new_data-=0x60;
+	}
+	else
+	{
+		if (flag(H) | ((data&0xf)>9)) new_data+=6;
+		if (flag(C) | (data>0x99)) new_data+=0x60;
+	}
+
+	set_flag_c(new_data & 0x100);
+	set_flag_s(new_data & 0x80);
+	new_data &= 0xff;
+	set_flag_z(new_data == 0);
+	// officially, v is undefined
+	register_write(dst, new_data);
 }
 
 INSTRUCTION( da_R1 )            { mode_R1(decimal_adjust) }