diff --git a/core/cpu.c b/core/cpu.c
index 9024966..386ddd2 100644
--- a/core/cpu.c
+++ b/core/cpu.c
@@ -1636,7 +1636,7 @@ static void cpuSUBF_S(VB *sim) {
 
 /* TRAP */
 static void cpuTRAP(VB *sim) {
-    sim->cpu.clocks += cpuClocks(15);
+    cpuAdvance(sim, cpuClocks(15));
     cpuThrow(sim, 0xFFA0 + cpuGetImm5U(sim));
 }
 
diff --git a/core/timer.c b/core/timer.c
index 892f5da..5e11ea6 100644
--- a/core/timer.c
+++ b/core/timer.c
@@ -117,7 +117,7 @@ static void tmrWriteControl(VB *sim, uint8_t value) {
     if (
         !sim->tmr.t_clk_sel &&
         (value & 0x10)      && /* T-Clk-Sel */
-        sim->tmr.tick20 != 4
+        sim->tmr.tick20 != 0
     ) {
         tmrUpdate(sim, sim->tmr.counter == 0 ?
             sim->tmr.reload : sim->tmr.counter - 1);