diff --git a/draw.cpp b/draw.cpp
index 13f85a1..1f59ff6 100644
--- a/draw.cpp
+++ b/draw.cpp
@@ -924,10 +924,8 @@ void GraphicsWindow::Paint(int w, int h) {
     } else {
         // Draw a red background whenever we're having solve problems.
         glClearColor(0.4f, 0, 0, 1.0f);
-        if(!showTextWindow) {
-            showTextWindow = true;
-            ShowTextWindow(TRUE);
-        }
+        // And show the text window, which has info to debug it
+        ForceTextWindowShown();
     }
 
     glClearDepth(1.0); 
diff --git a/graphicswin.cpp b/graphicswin.cpp
index af554c0..c2ca0c7 100644
--- a/graphicswin.cpp
+++ b/graphicswin.cpp
@@ -430,6 +430,14 @@ bool GraphicsWindow::LockedInWorkplane(void) {
     return (SS.GW.ActiveWorkplane().v != Entity::FREE_IN_3D.v);
 }
 
+void GraphicsWindow::ForceTextWindowShown(void) {
+    if(!showTextWindow) {
+        showTextWindow = true;
+        CheckMenuById(MNU_SHOW_TEXT_WND, true);
+        ShowTextWindow(TRUE);
+    }
+}
+
 void GraphicsWindow::MenuEdit(int id) {
     switch(id) {
         case MNU_UNSELECT_ALL:
diff --git a/solvespace.cpp b/solvespace.cpp
index a50a61d..52b73be 100644
--- a/solvespace.cpp
+++ b/solvespace.cpp
@@ -373,6 +373,10 @@ void SolveSpace::MenuAnalyze(int id) {
                     SS.TW.shown.constraint = c->h;
                     SS.TW.shown.screen = TextWindow::SCREEN_STEP_DIMENSION;
 
+                    // The step params are specified in the text window,
+                    // so force that to be shown.
+                    SS.GW.ForceTextWindowShown();
+
                     SS.later.showTW = true;
                     SS.GW.ClearSelection();
                 } else {
diff --git a/textscreens.cpp b/textscreens.cpp
index 5678ffd..8499273 100644
--- a/textscreens.cpp
+++ b/textscreens.cpp
@@ -929,13 +929,19 @@ void TextWindow::EditControlDone(char *s) {
             break;
         }
 
-        case EDIT_STEP_DIM_FINISH:
+        case EDIT_STEP_DIM_FINISH: {
+            Expr *e = Expr::From(s);
+            if(!e) {
+                Error("Not a valid number or expression: '%s'", s);
+                break;
+            }
             if(shown.dimIsDistance) {
-                shown.dimFinish = SS.StringToMm(s);
+                shown.dimFinish = SS.ExprToMm(e);
             } else {
-                shown.dimFinish = atof(s);
+                shown.dimFinish = e->Eval();
             }
             break;
+        }
 
         case EDIT_STEP_DIM_STEPS:
             shown.dimSteps = min(300, max(1, atoi(s)));
diff --git a/ui.h b/ui.h
index 1cd56e2..261cbec 100644
--- a/ui.h
+++ b/ui.h
@@ -292,6 +292,7 @@ public:
     bool LockedInWorkplane(void);
     void SetWorkplaneFreeIn3d(void);
     hEntity ActiveWorkplane(void);
+    void ForceTextWindowShown(void);
 
     // Operations that must be completed by doing something with the mouse
     // are noted here. These occupy the same space as the menu ids.