diff --git a/src/egui_app.rs b/src/egui_app.rs
index 760d913..1ea1409 100644
--- a/src/egui_app.rs
+++ b/src/egui_app.rs
@@ -105,7 +105,7 @@ impl epi::App for MathApp {
                 ui.label("- signum, min, max");
             });
 
-        let mut new_func_data: Vec<(String, bool)> = Vec::new();
+        let mut new_func_data: Vec<(String, bool, bool)> = Vec::new();
         let mut parse_error: String = "".to_string();
         egui::SidePanel::left("side_panel")
             .resizable(false)
@@ -132,11 +132,13 @@ impl epi::App for MathApp {
                     });
 
                     let func_test_output = test_func(func_str.clone());
+                    let mut got_error: bool = false;
                     if !func_test_output.is_empty() {
                         parse_error += &func_test_output;
+                        got_error = true;
                     }
 
-                    new_func_data.push((func_str, integral_toggle));
+                    new_func_data.push((func_str, integral_toggle, got_error));
                 }
 
                 let min_x_old = *min_x;
@@ -191,15 +193,16 @@ impl epi::App for MathApp {
 
                 let mut i: usize = 0;
                 for function in functions.iter_mut() {
-                    let (func_str, integral_toggle) = (new_func_data[i].0.clone(), new_func_data[i].1);
+                    let (func_str, integral_toggle, got_error) = (new_func_data[i].0.clone(), new_func_data[i].1, new_func_data[i].2);
+
                     let integral: bool = if integral_toggle {
                         !function.is_integral()
                     } else {
                         function.is_integral()
                     };
 
-                    
-                    function.update(func_str, *min_x, *max_x, integral, Some(*integral_min_x), Some(*integral_max_x), Some(*integral_num));
+
+                    function.update(func_str, *min_x, *max_x, integral, Some(*integral_min_x), Some(*integral_max_x), Some(*integral_num), got_error);
                     i += 1;
                 }
             });
@@ -218,6 +221,10 @@ impl epi::App for MathApp {
                 .include_y(0)
                 .show(ui, |plot_ui| {
                     for function in self.functions.iter_mut() {
+                        if function.is_broken() {
+                            continue;
+                        }
+
                         let output = function.run();
                         let back = output.get_back();
                         plot_ui.line(Line::new(Values::from_values(back)).color(Color32::RED));
diff --git a/src/function.rs b/src/function.rs
index e4967ce..e3e4c24 100644
--- a/src/function.rs
+++ b/src/function.rs
@@ -51,6 +51,7 @@ pub struct Function {
     integral_min_x: f64,
     integral_max_x: f64,
     integral_num: usize,
+    broken_state: bool,
 }
 
 impl Function {
@@ -91,6 +92,7 @@ impl Function {
                 Some(x) => x,
                 None => 0,
             },
+            broken_state: false,
         }
     }
 
@@ -102,7 +104,14 @@ impl Function {
     pub fn update(
         &mut self, func_str: String, min_x: f64, max_x: f64, integral: bool,
         integral_min_x: Option<f64>, integral_max_x: Option<f64>, integral_num: Option<usize>,
+        broken_state: bool,
     ) {
+        if broken_state {
+            self.func_str = func_str.clone();
+            self.broken_state = true;
+            return;
+        }
+
         // If the function string changes, just wipe and restart from scratch
         if func_str != self.func_str {
             *self = Self::new(
@@ -157,6 +166,9 @@ impl Function {
     #[inline]
     pub fn is_integral(&self) -> bool { self.integral }
 
+    #[inline]
+    pub fn is_broken(&self) -> bool { self.broken_state }
+
     #[inline]
     pub fn run(&mut self) -> FunctionOutput {
         let front_values: Vec<Value> = match self.back_cache.is_valid() {
@@ -208,6 +220,15 @@ impl Function {
         if !self.integral {
             panic!("integral_rectangles called, but self.integral is false!");
         }
+
+        if self.integral_min_x.is_nan() {
+            panic!("integral_min_x is NaN")
+        }
+
+        if self.integral_max_x.is_nan() {
+            panic!("integral_max_x is NaN")
+        }
+
         let step = self.get_step();
 
         let half_step = step / 2.0;