diff --git a/src/event.rs b/src/event.rs
index 4ae25860..f592da5c 100644
--- a/src/event.rs
+++ b/src/event.rs
@@ -106,7 +106,7 @@ impl<'a, N: Notify + 'a> input::ActionContext for ActionContext<'a, N> {
         self.terminal.pixels_to_coords(self.mouse.x as usize, self.mouse.y as usize)
     }
 
-    fn change_font_size(&mut self, delta: i8) {
+    fn change_font_size(&mut self, delta: f32) {
         self.terminal.change_font_size(delta);
     }
 
diff --git a/src/input.rs b/src/input.rs
index 2d603783..7afd359d 100644
--- a/src/input.rs
+++ b/src/input.rs
@@ -34,6 +34,8 @@ use term::SizeInfo;
 use term::mode::TermMode;
 use util::fmt::Red;
 
+pub const FONT_SIZE_STEP: f32 = 0.5;
+
 /// Processes input from glutin.
 ///
 /// An escape sequence may be emitted in case specific keys or key combinations
@@ -62,7 +64,7 @@ pub trait ActionContext {
     fn received_count(&mut self) -> &mut usize;
     fn suppress_chars(&mut self) -> &mut bool;
     fn last_modifiers(&mut self) -> &mut ModifiersState;
-    fn change_font_size(&mut self, delta: i8);
+    fn change_font_size(&mut self, delta: f32);
     fn reset_font_size(&mut self);
 }
 
@@ -227,10 +229,10 @@ impl Action {
                 ::std::process::exit(0);
             },
             Action::IncreaseFontSize => {
-               ctx.change_font_size(1);
+               ctx.change_font_size(FONT_SIZE_STEP);
             },
             Action::DecreaseFontSize => {
-               ctx.change_font_size(-1);
+               ctx.change_font_size(-FONT_SIZE_STEP);
             }
             Action::ResetFontSize => {
                ctx.reset_font_size();
@@ -698,7 +700,7 @@ mod tests {
         fn last_modifiers(&mut self) -> &mut ModifiersState {
             &mut self.last_modifiers
         }
-        fn change_font_size(&mut self, _delta: i8) {
+        fn change_font_size(&mut self, _delta: f32) {
         }
         fn reset_font_size(&mut self) {
         }
diff --git a/src/term/mod.rs b/src/term/mod.rs
index 4f56e7fc..27cc9312 100644
--- a/src/term/mod.rs
+++ b/src/term/mod.rs
@@ -30,6 +30,7 @@ use selection::{self, Span, Selection};
 use config::{Config, VisualBellAnimation};
 use {MouseCursor, Rgb};
 use copypasta::{Clipboard, Load, Store};
+use input::FONT_SIZE_STEP;
 
 pub mod cell;
 pub mod color;
@@ -841,10 +842,10 @@ impl Term {
         }
     }
 
-    pub fn change_font_size(&mut self, delta: i8) {
-        // Saturating addition with minimum font size 1
-        let new_size = self.font_size + Size::new(f32::from(delta));
-        self.font_size = max(new_size, Size::new(1.));
+    pub fn change_font_size(&mut self, delta: f32) {
+        // Saturating addition with minimum font size FONT_SIZE_STEP
+        let new_size = self.font_size + Size::new(delta);
+        self.font_size = max(new_size, Size::new(FONT_SIZE_STEP));
         self.dirty = true;
     }
 
@@ -1947,6 +1948,9 @@ mod tests {
     use ansi::{Handler, CharsetIndex, StandardCharset};
     use selection::Selection;
     use std::mem;
+    use input::FONT_SIZE_STEP;
+    use font::Size;
+    use config::Config;
 
     #[test]
     fn semantic_selection_works() {
@@ -2052,6 +2056,72 @@ mod tests {
 
         assert_eq!(term.grid()[&cursor].c, '▒');
     }
+
+    fn change_font_size_works(font_size: f32) {
+        let size = SizeInfo {
+            width: 21.0,
+            height: 51.0,
+            cell_width: 3.0,
+            cell_height: 3.0,
+            padding_x: 0.0,
+            padding_y: 0.0,
+        };
+        let config: Config = Default::default();
+        let mut term: Term = Term::new(&config, size);
+        term.change_font_size(font_size);
+
+        let expected_font_size: Size = config.font().size() + Size::new(font_size);
+        assert_eq!(term.font_size, expected_font_size);
+    }
+
+    #[test]
+    fn increase_font_size_works() {
+        change_font_size_works(10.0);
+    }
+
+    #[test]
+    fn decrease_font_size_works() {
+        change_font_size_works(-10.0);
+    }
+
+    #[test]
+    fn prevent_font_below_threshold_works() {
+        let size = SizeInfo {
+            width: 21.0,
+            height: 51.0,
+            cell_width: 3.0,
+            cell_height: 3.0,
+            padding_x: 0.0,
+            padding_y: 0.0,
+        };
+        let config: Config = Default::default();
+        let mut term: Term = Term::new(&config, size);
+
+        term.change_font_size(-100.0);
+
+        let expected_font_size: Size = Size::new(FONT_SIZE_STEP);
+        assert_eq!(term.font_size, expected_font_size);
+    }
+
+    #[test]
+    fn reset_font_size_works() {
+        let size = SizeInfo {
+            width: 21.0,
+            height: 51.0,
+            cell_width: 3.0,
+            cell_height: 3.0,
+            padding_x: 0.0,
+            padding_y: 0.0,
+        };
+        let config: Config = Default::default();
+        let mut term: Term = Term::new(&config, size);
+
+        term.change_font_size(10.0);
+        term.reset_font_size();
+
+        let expected_font_size: Size = config.font().size();
+        assert_eq!(term.font_size, expected_font_size);
+    }
 }
 
 #[cfg(all(test, feature = "bench"))]