diff --git a/jGui b/jGui
index 4125b3ac..163cfe2f 160000
--- a/jGui
+++ b/jGui
@@ -1 +1 @@
-Subproject commit 4125b3ac207b7afee753c0503e07f8f7899a9950
+Subproject commit 163cfe2f8a9caa6792dc262c139afc066d371cfb
diff --git a/src/main/java/com/replaymod/simplepathing/gui/GuiKeyframeTimeline.java b/src/main/java/com/replaymod/simplepathing/gui/GuiKeyframeTimeline.java
index 2ca6ba72..72f1368c 100644
--- a/src/main/java/com/replaymod/simplepathing/gui/GuiKeyframeTimeline.java
+++ b/src/main/java/com/replaymod/simplepathing/gui/GuiKeyframeTimeline.java
@@ -121,24 +121,42 @@ public class GuiKeyframeTimeline extends AbstractGuiTimeline<GuiKeyframeTimeline
                     || !segment.getInterpolator().getKeyframeProperties().contains(SpectatorProperty.PROPERTY)) {
                 continue; // Not a spectator segment
             }
-            long startFrameTime = segment.getStartKeyframe().getTime();
-            long endFrameTime = segment.getEndKeyframe().getTime();
-            if (startFrameTime >= endTime || endFrameTime <= startTime) {
-                continue; // Segment out of display range
-            }
+            drawQuadOnSegment(renderer, visibleWidth, segment, BORDER_TOP + 1, 0xFF0088FF);
+        }
 
-            double relativeStart = startFrameTime - startTime;
-            double relativeEnd = endFrameTime - startTime;
-            int startX = BORDER_LEFT + Math.max(0, (int) (relativeStart / visibleTime * visibleWidth) + KEYFRAME_SIZE / 2 + 1);
-            int endX = BORDER_LEFT + Math.min(visibleWidth, (int) (relativeEnd / visibleTime * visibleWidth) - KEYFRAME_SIZE / 2);
-            if (startX < endX) {
-                renderer.drawRect(startX + 1, BORDER_TOP + 1, endX - startX - 2, KEYFRAME_SIZE - 2, 0xFF0088FF);
+        // Draw red quads on time path segments that would require time going backwards
+        for (PathSegment segment : mod.getCurrentTimeline().getPaths().get(GuiPathing.TIME_PATH).getSegments()) {
+            long startTimestamp = segment.getStartKeyframe().getValue(TimestampProperty.PROPERTY).orElseThrow(IllegalStateException::new);
+            long endTimestamp = segment.getEndKeyframe().getValue(TimestampProperty.PROPERTY).orElseThrow(IllegalStateException::new);
+            if (endTimestamp >= startTimestamp) {
+                continue; // All is fine, time is not moving backwards
             }
+            drawQuadOnSegment(renderer, visibleWidth, segment, BORDER_TOP + KEYFRAME_SIZE + 1, 0xFFFF0000);
         }
 
         super.drawTimelineCursor(renderer, size);
     }
 
+    private void drawQuadOnSegment(GuiRenderer renderer, int visibleWidth, PathSegment segment, int y, int color) {
+        int startTime = getOffset();
+        int visibleTime = (int) (getZoom() * getLength());
+        int endTime = getOffset() + visibleTime;
+
+        long startFrameTime = segment.getStartKeyframe().getTime();
+        long endFrameTime = segment.getEndKeyframe().getTime();
+        if (startFrameTime >= endTime || endFrameTime <= startTime) {
+            return; // Segment out of display range
+        }
+
+        double relativeStart = startFrameTime - startTime;
+        double relativeEnd = endFrameTime - startTime;
+        int startX = BORDER_LEFT + Math.max(0, (int) (relativeStart / visibleTime * visibleWidth) + KEYFRAME_SIZE / 2 + 1);
+        int endX = BORDER_LEFT + Math.min(visibleWidth, (int) (relativeEnd / visibleTime * visibleWidth) - KEYFRAME_SIZE / 2);
+        if (startX < endX) {
+            renderer.drawRect(startX + 1, y, endX - startX - 2, KEYFRAME_SIZE - 2, color);
+        }
+    }
+
     /**
      * Returns the keyframe at the specified position.
      * @param position The raw position
diff --git a/src/main/java/com/replaymod/simplepathing/gui/GuiPathing.java b/src/main/java/com/replaymod/simplepathing/gui/GuiPathing.java
index ab8aae28..8e0236b1 100644
--- a/src/main/java/com/replaymod/simplepathing/gui/GuiPathing.java
+++ b/src/main/java/com/replaymod/simplepathing/gui/GuiPathing.java
@@ -38,6 +38,7 @@ import de.johni0702.minecraft.gui.layout.CustomLayout;
 import de.johni0702.minecraft.gui.layout.HorizontalLayout;
 import de.johni0702.minecraft.gui.layout.VerticalLayout;
 import de.johni0702.minecraft.gui.popup.AbstractGuiPopup;
+import de.johni0702.minecraft.gui.popup.GuiInfoPopup;
 import de.johni0702.minecraft.gui.popup.GuiYesNoPopup;
 import de.johni0702.minecraft.gui.utils.Colors;
 import net.minecraft.entity.Entity;
@@ -75,7 +76,7 @@ public class GuiPathing {
     public final GuiTexturedButton renderButton = new GuiTexturedButton().onClick(new Runnable() {
         @Override
         public void run() {
-            preparePathsForPlayback();
+            if (!preparePathsForPlayback()) return;
             new GuiRenderSettings(replayHandler, mod.getCurrentTimeline()).display();
         }
     }).setSize(20, 20).setTexture(ReplayMod.TEXTURE, ReplayMod.TEXTURE_SIZE).setTexturePosH(40, 0);
@@ -231,7 +232,7 @@ public class GuiPathing {
                     Timeline timeline = mod.getCurrentTimeline();
                     Path timePath = timeline.getPaths().get(TIME_PATH);
 
-                    preparePathsForPlayback();
+                    if (!preparePathsForPlayback()) return;
 
                     timePath.setActive(!Keyboard.isKeyDown(Keyboard.KEY_LSHIFT));
                     ListenableFuture<Void> future = player.start(timeline);
@@ -438,10 +439,27 @@ public class GuiPathing {
         }).start();
     }
 
-    private void preparePathsForPlayback() {
+    private boolean preparePathsForPlayback() {
         Timeline timeline = mod.getCurrentTimeline();
         timeline.getPaths().get(TIME_PATH).updateAll();
         timeline.getPaths().get(POSITION_PATH).updateAll();
+
+        // Make sure time keyframes's values are monotonically increasing
+        int lastTime = 0;
+        for (Keyframe keyframe : timeline.getPaths().get(TIME_PATH).getKeyframes()) {
+            int time = keyframe.getValue(TimestampProperty.PROPERTY).orElseThrow(IllegalStateException::new);
+            if (time < lastTime) {
+                // We are going backwards in time
+                GuiInfoPopup.open(replayHandler.getOverlay(),
+                        "replaymod.error.negativetime1",
+                        "replaymod.error.negativetime2",
+                        "replaymod.error.negativetime3");
+                return false;
+            }
+            lastTime = time;
+        }
+
+        return true;
     }
 
     public void zoomTimeline(double factor) {
diff --git a/src/main/resources/assets/replaymod/lang/en_US.lang b/src/main/resources/assets/replaymod/lang/en_US.lang
index 1c660296..ecdf54ef 100644
--- a/src/main/resources/assets/replaymod/lang/en_US.lang
+++ b/src/main/resources/assets/replaymod/lang/en_US.lang
@@ -485,6 +485,9 @@ replaymod.gui.objects=Custom Objects
 #Errors
 replaymod.error.unknownrestriction1=This replay cannot be played with your current version.
 replaymod.error.unknownrestriction2=It tried to enforce %s which is unknown.
+replaymod.error.negativetime1=Some of your time keyframes are out of order.
+replaymod.error.negativetime2=Going backwards in time is not supported.
+replaymod.error.negativetime3=The invalid parts are marked in red.
 
 #Replay Mod Incompatibility Warning
 replaymod.gui.modwarning.title=Incompatibility detected