diff --git a/src/commands/verify_program.rs b/src/commands/verify_program.rs
index ae2e482..1f35cc9 100644
--- a/src/commands/verify_program.rs
+++ b/src/commands/verify_program.rs
@@ -1,4 +1,5 @@
-pub fn run<P>(program_path: P, specification_path: P, proof_direction: crate::ProofDirection)
+pub fn run<P>(program_path: P, specification_path: P, proof_direction:
+	crate::problem::ProofDirection)
 where
 	P: AsRef<std::path::Path>
 {
diff --git a/src/input/specification.rs b/src/input/specification.rs
index db5d67e..e03373a 100644
--- a/src/input/specification.rs
+++ b/src/input/specification.rs
@@ -349,15 +349,15 @@ pub(crate) fn parse_specification(mut input: &str, problem: &crate::Problem)
 							foliage::parse::tokens::identifier(input)
 						{
 							Some(("forward", remaining_input)) =>
-								(crate::ProofDirection::Forward, remaining_input),
+								(crate::problem::ProofDirection::Forward, remaining_input),
 							Some(("backward", remaining_input)) =>
-								(crate::ProofDirection::Backward, remaining_input),
+								(crate::problem::ProofDirection::Backward, remaining_input),
 							Some(("both", remaining_input)) =>
-								(crate::ProofDirection::Both, remaining_input),
+								(crate::problem::ProofDirection::Both, remaining_input),
 							Some((identifier, _)) =>
 								return Err(crate::Error::new_unknown_proof_direction(
 									identifier.to_string())),
-							None => (crate::ProofDirection::Both, input),
+							None => (crate::problem::ProofDirection::Both, input),
 						};
 
 						input = remaining_input.trim_start();
@@ -374,7 +374,7 @@ pub(crate) fn parse_specification(mut input: &str, problem: &crate::Problem)
 						(proof_direction, input)
 					},
 					Some(_)
-					| None => (crate::ProofDirection::Both, remaining_input),
+					| None => (crate::problem::ProofDirection::Both, remaining_input),
 				};
 
 				input = remaining_input;
diff --git a/src/lib.rs b/src/lib.rs
index 1ab2abf..0c0845f 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -12,4 +12,4 @@ mod utils;
 pub use error::Error;
 pub use problem::Problem;
 pub(crate) use utils::*;
-pub use utils::{Domain, InputConstantDeclarationDomains, ProofDirection};
+pub use utils::{Domain, InputConstantDeclarationDomains};
diff --git a/src/main.rs b/src/main.rs
index 752128e..ed5c583 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -18,7 +18,7 @@ enum Command
 
 		/// Proof direction (forward, backward, both)
 		#[structopt(long, default_value = "forward")]
-		proof_direction: anthem::ProofDirection,
+		proof_direction: anthem::problem::ProofDirection,
 	}
 }
 
diff --git a/src/problem.rs b/src/problem.rs
index 6c549b1..91c4419 100644
--- a/src/problem.rs
+++ b/src/problem.rs
@@ -1,5 +1,7 @@
+mod proof_direction;
 mod section_kind;
 
+pub use proof_direction::ProofDirection;
 pub use section_kind::SectionKind;
 
 #[derive(Copy, Clone, Eq, PartialEq)]
@@ -8,7 +10,7 @@ pub enum StatementKind
 	Axiom,
 	Program,
 	Assumption,
-	Lemma(crate::ProofDirection),
+	Lemma(ProofDirection),
 	Assertion,
 }
 
@@ -124,10 +126,10 @@ impl Problem
 		section.push(statement);
 	}
 
-	pub fn prove(&self, proof_direction: crate::ProofDirection) -> Result<(), crate::Error>
+	pub fn prove(&self, proof_direction: ProofDirection) -> Result<(), crate::Error>
 	{
-		if proof_direction == crate::ProofDirection::Forward
-			|| proof_direction == crate::ProofDirection::Both
+		if proof_direction == ProofDirection::Forward
+			|| proof_direction == ProofDirection::Both
 		{
 			println!("performing forward proof");
 
@@ -144,7 +146,7 @@ impl Problem
 						| StatementKind::Assumption
 						| StatementKind::Program =>
 							statement.proof_status = ProofStatus::AssumedProven,
-						StatementKind::Lemma(crate::ProofDirection::Backward) =>
+						StatementKind::Lemma(ProofDirection::Backward) =>
 							statement.proof_status = ProofStatus::Ignored,
 						_ => statement.proof_status = ProofStatus::ToProveLater,
 					}
@@ -158,8 +160,8 @@ impl Problem
 			println!("finished forward proof");
 		}
 
-		if proof_direction == crate::ProofDirection::Backward
-			|| proof_direction == crate::ProofDirection::Both
+		if proof_direction == ProofDirection::Backward
+			|| proof_direction == ProofDirection::Both
 		{
 			println!("performing backward proof");
 
@@ -176,7 +178,7 @@ impl Problem
 						| StatementKind::Assumption
 						| StatementKind::Assertion =>
 							statement.proof_status = ProofStatus::AssumedProven,
-						StatementKind::Lemma(crate::ProofDirection::Forward) =>
+						StatementKind::Lemma(ProofDirection::Forward) =>
 							statement.proof_status = ProofStatus::Ignored,
 						_ => statement.proof_status = ProofStatus::ToProveLater,
 					}
diff --git a/src/problem/proof_direction.rs b/src/problem/proof_direction.rs
new file mode 100644
index 0000000..0f586a9
--- /dev/null
+++ b/src/problem/proof_direction.rs
@@ -0,0 +1,62 @@
+#[derive(Clone, Copy, Eq, Hash, PartialEq)]
+pub enum ProofDirection
+{
+	Forward,
+	Backward,
+	Both,
+}
+
+impl std::fmt::Debug for ProofDirection
+{
+	fn fmt(&self, formatter: &mut std::fmt::Formatter) -> std::fmt::Result
+	{
+		match self
+		{
+			ProofDirection::Forward => write!(formatter, "forward"),
+			ProofDirection::Backward => write!(formatter, "backward"),
+			ProofDirection::Both => write!(formatter, "both"),
+		}
+	}
+}
+
+impl std::fmt::Display for ProofDirection
+{
+	fn fmt(&self, formatter: &mut std::fmt::Formatter) -> std::fmt::Result
+	{
+		write!(formatter, "{:?}", self)
+	}
+}
+
+pub struct InvalidProofDirectionError;
+
+impl std::fmt::Debug for InvalidProofDirectionError
+{
+	fn fmt(&self, formatter: &mut std::fmt::Formatter) -> std::fmt::Result
+	{
+		write!(formatter, "invalid proof direction")
+	}
+}
+
+impl std::fmt::Display for InvalidProofDirectionError
+{
+	fn fmt(&self, formatter: &mut std::fmt::Formatter) -> std::fmt::Result
+	{
+		write!(formatter, "{:?}", self)
+	}
+}
+
+impl std::str::FromStr for ProofDirection
+{
+	type Err = InvalidProofDirectionError;
+
+	fn from_str(s: &str) -> Result<Self, Self::Err>
+	{
+		match s
+		{
+			"forward" => Ok(ProofDirection::Forward),
+			"backward" => Ok(ProofDirection::Backward),
+			"both" => Ok(ProofDirection::Both),
+			_ => Err(InvalidProofDirectionError),
+		}
+	}
+}
diff --git a/src/utils.rs b/src/utils.rs
index 48f07b5..1d73d33 100644
--- a/src/utils.rs
+++ b/src/utils.rs
@@ -38,69 +38,6 @@ impl std::fmt::Display for Domain
 	}
 }
 
-#[derive(Clone, Copy, Eq, Hash, PartialEq)]
-pub enum ProofDirection
-{
-	Forward,
-	Backward,
-	Both,
-}
-
-impl std::fmt::Debug for ProofDirection
-{
-	fn fmt(&self, formatter: &mut std::fmt::Formatter) -> std::fmt::Result
-	{
-		match self
-		{
-			ProofDirection::Forward => write!(formatter, "forward"),
-			ProofDirection::Backward => write!(formatter, "backward"),
-			ProofDirection::Both => write!(formatter, "both"),
-		}
-	}
-}
-
-impl std::fmt::Display for ProofDirection
-{
-	fn fmt(&self, formatter: &mut std::fmt::Formatter) -> std::fmt::Result
-	{
-		write!(formatter, "{:?}", self)
-	}
-}
-
-pub struct InvalidProofDirectionError;
-
-impl std::fmt::Debug for InvalidProofDirectionError
-{
-	fn fmt(&self, formatter: &mut std::fmt::Formatter) -> std::fmt::Result
-	{
-		write!(formatter, "invalid proof direction")
-	}
-}
-
-impl std::fmt::Display for InvalidProofDirectionError
-{
-	fn fmt(&self, formatter: &mut std::fmt::Formatter) -> std::fmt::Result
-	{
-		write!(formatter, "{:?}", self)
-	}
-}
-
-impl std::str::FromStr for ProofDirection
-{
-	type Err = InvalidProofDirectionError;
-
-	fn from_str(s: &str) -> Result<Self, Self::Err>
-	{
-		match s
-		{
-			"forward" => Ok(ProofDirection::Forward),
-			"backward" => Ok(ProofDirection::Backward),
-			"both" => Ok(ProofDirection::Both),
-			_ => Err(InvalidProofDirectionError),
-		}
-	}
-}
-
 pub(crate) struct ScopedFormula
 {
 	pub free_variable_declarations: std::rc::Rc<foliage::VariableDeclarations>,