diff --git a/compiler/ast/src/functions/input/function_input.rs b/compiler/ast/src/functions/input/function_input.rs
index 0da279d029..4aa10eec78 100644
--- a/compiler/ast/src/functions/input/function_input.rs
+++ b/compiler/ast/src/functions/input/function_input.rs
@@ -20,17 +20,32 @@ use leo_span::Span;
 use serde::{Deserialize, Serialize};
 use std::fmt;
 
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
+pub enum ParamMode {
+    Const,
+    Private,
+    Public,
+}
+
+impl fmt::Display for ParamMode {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        use ParamMode::*;
+
+        match self {
+            Const => write!(f, "const"),
+            Private => write!(f, "private"),
+            Public => write!(f, "public"),
+        }
+    }
+}
+
 /// A function parameter.
 #[derive(Clone, PartialEq, Eq, Serialize, Deserialize)]
 pub struct FunctionInputVariable {
     /// The name the parameter is accessible as in the function's body.
     pub identifier: Identifier,
     /// Is it a const parameter?
-    pub const_: bool,
-    /// Is it a public parameter?
-    pub public: bool,
-    /// Is it a mutable parameter?
-    pub mutable: bool,
+    pub mode: ParamMode,
     /// What's the parameter's type?
     pub type_: Type,
     /// The parameters span from any annotations to its type.
@@ -39,17 +54,7 @@ pub struct FunctionInputVariable {
 
 impl FunctionInputVariable {
     fn format(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        if self.public {
-            write!(f, "public ")?;
-        } else {
-            write!(f, "private ")?;
-        }
-        if self.const_ {
-            write!(f, "const ")?;
-        }
-        if self.mutable {
-            write!(f, "mut ")?;
-        }
+        write!(f, "{} ", self.mode)?;
         write!(f, "{}: ", self.identifier)?;
         write!(f, "{}", self.type_)
     }
diff --git a/compiler/ast/src/input/definition.rs b/compiler/ast/src/input/definition.rs
index 9090111b5e..6be63b04d3 100644
--- a/compiler/ast/src/input/definition.rs
+++ b/compiler/ast/src/input/definition.rs
@@ -15,14 +15,13 @@
 // along with the Leo library. If not, see <https://www.gnu.org/licenses/>.
 
 use super::*;
-use crate::{Expression, Identifier, Type};
+use crate::{Expression, Identifier, ParamMode, Type};
 
 /// A single definition inside a section in a state or an input file.
 /// Definitions should be structured as: `<name>: <type_> = <value>;`
 #[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
 pub struct Definition {
-    pub const_: bool,
-    pub public: bool,
+    pub mode: ParamMode,
     pub type_: Type,
     pub name: Identifier,
     pub value: Expression,
diff --git a/compiler/ast/src/reducer/reconstructing_reducer.rs b/compiler/ast/src/reducer/reconstructing_reducer.rs
index 1af16ec488..d47053ad4e 100644
--- a/compiler/ast/src/reducer/reconstructing_reducer.rs
+++ b/compiler/ast/src/reducer/reconstructing_reducer.rs
@@ -274,9 +274,7 @@ pub trait ReconstructingReducer {
     ) -> Result<FunctionInputVariable> {
         Ok(FunctionInputVariable {
             identifier,
-            const_: variable.const_,
-            mutable: variable.mutable,
-            public: variable.public,
+            mode: variable.mode,
             type_,
             span: variable.span.clone(),
         })
diff --git a/compiler/parser/src/parser/file.rs b/compiler/parser/src/parser/file.rs
index 8fc836d74e..effb6b13a3 100644
--- a/compiler/parser/src/parser/file.rs
+++ b/compiler/parser/src/parser/file.rs
@@ -61,12 +61,23 @@ impl ParserContext<'_> {
         )
     }
 
+    pub fn parse_function_parameter_mode(&mut self) -> Result<ParamMode> {
+        let public = self.eat(Token::Public);
+        let const_ = self.eat(Token::Const);
+
+        match (public, const_) {
+            (None, Some(_)) => Ok(ParamMode::Const),
+            (None, None) => Ok(ParamMode::Private),
+            (Some(_), None) => Ok(ParamMode::Public),
+            (Some(p), Some(c)) => Err(ParserError::inputs_multiple_variable_types_specified(&(p.span + c.span)).into()),
+        }
+    }
+
     ///
     /// Returns a [`FunctionInput`] AST node if the next tokens represent a function parameter.
     ///
     pub fn parse_function_parameters(&mut self) -> Result<FunctionInput> {
-        let public = self.eat(Token::Public).is_some();
-        let const_ = self.eat(Token::Const);
+        let mode = self.parse_function_parameter_mode()?;
         let mutable = self.eat(Token::Mut);
 
         let name = self.expect_ident()?;
@@ -78,9 +89,7 @@ impl ParserContext<'_> {
         self.expect(Token::Colon)?;
         let type_ = self.parse_type()?.0;
         Ok(FunctionInput::Variable(FunctionInputVariable {
-            const_: const_.is_some(),
-            mutable: const_.is_none(),
-            public,
+            mode,
             type_,
             span: name.span.clone(),
             identifier: name,
diff --git a/compiler/parser/src/parser/input.rs b/compiler/parser/src/parser/input.rs
index 8750b7d3c3..2c0b68d6f8 100644
--- a/compiler/parser/src/parser/input.rs
+++ b/compiler/parser/src/parser/input.rs
@@ -67,8 +67,7 @@ impl ParserContext<'_> {
     /// `<identifier> : <type> = <expression>;`
     /// Returns [`Definition`].
     pub fn parse_input_definition(&mut self) -> Result<Definition> {
-        let public = self.eat(Token::Public).is_some();
-        let const_ = self.eat(Token::Const).is_some();
+        let mode = self.parse_function_parameter_mode()?;
 
         let name = self.expect_ident()?;
         self.expect(Token::Colon)?;
@@ -78,8 +77,7 @@ impl ParserContext<'_> {
         self.expect(Token::Semicolon)?;
 
         Ok(Definition {
-            const_,
-            public,
+            mode,
             name,
             type_,
             value,
diff --git a/leo/errors/src/parser/parser_errors.rs b/leo/errors/src/parser/parser_errors.rs
index 9ce55319ca..217e305152 100644
--- a/leo/errors/src/parser/parser_errors.rs
+++ b/leo/errors/src/parser/parser_errors.rs
@@ -358,4 +358,12 @@ create_errors!(
         msg: format!("Found the char `{}`, but expected `{}`", found, expected),
         help: None,
     }
+
+     /// For when a user specified more than a type on a parameter.
+     @formatted
+     inputs_multiple_variable_types_specified {
+         args: (),
+         msg: "A parameter cannot be both public and const.",
+         help: None,
+     }
 );
diff --git a/leo/span/src/symbol.rs b/leo/span/src/symbol.rs
index 20d0b91200..095f0f83b6 100644
--- a/leo/span/src/symbol.rs
+++ b/leo/span/src/symbol.rs
@@ -131,7 +131,7 @@ symbols! {
     main,
     Mut: "mut",
     prelude,
-    Public: "public",
+    Public,
     Return: "return",
     Star: "*",
     std,