diff --git a/src/spectator/matchers/alternative_match_data_value.cr b/src/spectator/matchers/alternative_match_data_value.cr
index 49e904a..e368c0f 100644
--- a/src/spectator/matchers/alternative_match_data_value.cr
+++ b/src/spectator/matchers/alternative_match_data_value.cr
@@ -21,7 +21,7 @@ module Spectator::Matchers
 
     # Produces a stringified value.
     def to_s(io)
-      io << value
+      @value.inspect(io)
     end
 
     # Produces a stringified value with additional information.
diff --git a/src/spectator/matchers/generic_match_data_value.cr b/src/spectator/matchers/generic_match_data_value.cr
index 3d751f9..9069489 100644
--- a/src/spectator/matchers/generic_match_data_value.cr
+++ b/src/spectator/matchers/generic_match_data_value.cr
@@ -12,7 +12,7 @@ module Spectator::Matchers
 
     # Stringifies the value.
     def to_s(io)
-      io << @value
+      @value.inspect(io)
     end
 
     # Inspects the value.
diff --git a/src/spectator/matchers/negatable_match_data_value.cr b/src/spectator/matchers/negatable_match_data_value.cr
index ac764fe..62abf49 100644
--- a/src/spectator/matchers/negatable_match_data_value.cr
+++ b/src/spectator/matchers/negatable_match_data_value.cr
@@ -21,7 +21,7 @@ module Spectator::Matchers
     # The string will be prefixed with "Not" when negated.
     def to_s(io)
       io << "Not " if @negated
-      io << @value
+      @value.inspect(io)
     end
 
     # Produces a stringified value with additional information.
diff --git a/src/spectator/matchers/negatable_prefixed_match_data_value.cr b/src/spectator/matchers/negatable_prefixed_match_data_value.cr
index f4cf4ea..9cc6138 100644
--- a/src/spectator/matchers/negatable_prefixed_match_data_value.cr
+++ b/src/spectator/matchers/negatable_prefixed_match_data_value.cr
@@ -26,7 +26,7 @@ module Spectator::Matchers
     def to_s(io)
       io << prefix
       io << ' '
-      io << @value
+      @value.inspect(io)
     end
 
     # Produces a stringified value with additional information.
diff --git a/src/spectator/matchers/prefixed_match_data_value.cr b/src/spectator/matchers/prefixed_match_data_value.cr
index 1e22002..feea8cc 100644
--- a/src/spectator/matchers/prefixed_match_data_value.cr
+++ b/src/spectator/matchers/prefixed_match_data_value.cr
@@ -14,7 +14,7 @@ module Spectator::Matchers
     def to_s(io)
       io << @prefix
       io << ' '
-      io << @value
+      @value.inspect(io)
     end
 
     # Outputs details of the formatted value with a prefix.