diff --git a/src/codegen/codegen_accumulate_x86-64.c b/src/codegen/codegen_accumulate_x86-64.c
index 45ec96684..d81c7dd83 100644
--- a/src/codegen/codegen_accumulate_x86-64.c
+++ b/src/codegen/codegen_accumulate_x86-64.c
@@ -26,7 +26,7 @@ void codegen_accumulate(int acc_reg, int delta)
 		addbyte(0x04);
 		addbyte(0x25);
 		addlong((uint32_t) (uintptr_t) &(acycs));
-		addlong(delta);
+		addlong(-delta);
 	}
 }
 
diff --git a/src/codegen/codegen_accumulate_x86.c b/src/codegen/codegen_accumulate_x86.c
index e577d913d..a897c942a 100644
--- a/src/codegen/codegen_accumulate_x86.c
+++ b/src/codegen/codegen_accumulate_x86.c
@@ -25,7 +25,7 @@ void codegen_accumulate(int acc_reg, int delta)
 		addbyte(0x81); /*ADD $acc_regs[c].count,acc_regs[c].dest*/
 		addbyte(0x05);
 		addlong((uint32_t) (uintptr_t) &(acycs));
-		addlong((uintptr_t) delta);
+		addlong((uintptr_t) -delta);
 	}
 }
 
diff --git a/src/codegen_new/codegen_accumulate.c b/src/codegen_new/codegen_accumulate.c
index 3b71d78d7..d307f3102 100644
--- a/src/codegen_new/codegen_accumulate.c
+++ b/src/codegen_new/codegen_accumulate.c
@@ -22,7 +22,7 @@ void codegen_accumulate(ir_data_t *ir, int acc_reg, int delta)
         acc_regs[acc_reg].count += delta;
 
 	if (delta != 0) {
-		uop_ADD_IMM(ir, IREG_acycs, IREG_acycs, delta);
+		uop_ADD_IMM(ir, IREG_acycs, IREG_acycs, -delta);
 	}
 }
 
diff --git a/src/cpu/386_dynarec.c b/src/cpu/386_dynarec.c
index 37aa81f00..4d0b43402 100644
--- a/src/cpu/386_dynarec.c
+++ b/src/cpu/386_dynarec.c
@@ -296,7 +296,8 @@ void update_tsc(void)
 		tsc += cycdiff;
     } else {
 	/* TSC has not changed. */
-	tsc += cycdiff;
+	if (cycdiff > 0)
+		tsc += cycdiff;
     }
 
     if (cycdiff > 0) {