diff --git a/compiler/add_foreign_enum.m b/compiler/add_foreign_enum.m
index f119043e8..042c3f44d 100644
--- a/compiler/add_foreign_enum.m
+++ b/compiler/add_foreign_enum.m
@@ -136,7 +136,7 @@ add_pragma_foreign_enum(ModuleInfo, ImsItem, !TypeCtorForeignEnumMap,
         OoMMercuryForeignTagPairs, Context, _SeqNum),
     % Here we construct ItemPragmaInfo just to test whether this pragma
     % was in the interface. Unfortunately, while we *could* avoid this
-    % (e.g. by making making report_if_pragma_is_wrongly_in_interface work
+    % (e.g. by making report_if_pragma_is_wrongly_in_interface work
     % not on full pragmas but on pragma kinds, a flattened-to-an-enum
     % form of pragmas), the cost in increased code complexity is
     % not worth it.
diff --git a/compiler/check_parse_tree_type_defns.m b/compiler/check_parse_tree_type_defns.m
index 039f3452b..69946672e 100644
--- a/compiler/check_parse_tree_type_defns.m
+++ b/compiler/check_parse_tree_type_defns.m
@@ -712,7 +712,7 @@ check_type_ctor_defns(InsistOnDefn, ModuleName,
         % TypeCtor is NOT defined as a solver, equivalence, du or foreign type,
         % and it is NOT declared either as a solver or as a nonsolver type.
         % This means it has no type definition whatsoever. The only way
-        % we can get here is is it has any foreign enum definitions.
+        % we can get here is if it has any foreign enum definitions.
         list.foldl(
             report_foreign_enum_for_undefined_type(TypeCtor, "undeclared"),
             ImpEnums, !Specs)
diff --git a/compiler/check_typeclass.m b/compiler/check_typeclass.m
index 05e46fa40..b12aa597a 100644
--- a/compiler/check_typeclass.m
+++ b/compiler/check_typeclass.m
@@ -459,7 +459,7 @@ bad_instance_type_msg(ClassId, InstanceDefn, EndPieces, Kind) = Spec :-
         % would not make sense.
         InstanceTypes = InstanceDefn ^ instdefn_orig_types
     ),
-    % XXX Removing the module qualification from the type type constructors
+    % XXX Removing the module qualification from the type constructors
     % in InstanceTypes before converting them to strings would make
     % the error message less cluttered.
     InstanceTypesString = mercury_type_list_to_string(InstanceVarSet,
diff --git a/compiler/dead_proc_elim.m b/compiler/dead_proc_elim.m
index cfca1f86d..b6048af9d 100644
--- a/compiler/dead_proc_elim.m
+++ b/compiler/dead_proc_elim.m
@@ -903,7 +903,7 @@ do_dead_proc_eliminate(ElimOptImported, !.Needed, !ModuleInfo) :-
         TypeCtorGenInfos),
     module_info_set_type_ctor_gen_infos(TypeCtorGenInfos, !ModuleInfo),
 
-    % We could also eliminate eliminate table structs, but we don't do that
+    % We could also eliminate table structs, but we don't do that
     % yet, because some references to such structs are currently visible
     % only in C code embedded in compiler-generated foreign_procs, and
     % therefore we might accidentally create dangling references.
diff --git a/compiler/exception_analysis.m b/compiler/exception_analysis.m
index 5cd11e1ad..a8ee8ec31 100644
--- a/compiler/exception_analysis.m
+++ b/compiler/exception_analysis.m
@@ -382,7 +382,7 @@ check_goal_for_exceptions_2(SCC, VarTypes, GoalExpr, GoalInfo,
     ;
         GoalExpr = call_foreign_proc(Attributes, _, _, _, _, _, _),
 
-        % NOTE: for --intermodule-analysis the results for for foreign_procs
+        % NOTE: for --intermodule-analysis the results for foreign_procs
         % will *always* be optimal (since we always rely on user annotation),
         % so there's nothing to do here.
         MayCallMercury = get_may_call_mercury(Attributes),
diff --git a/compiler/unused_args.m b/compiler/unused_args.m
index 669e4461e..fbdb7edc2 100644
--- a/compiler/unused_args.m
+++ b/compiler/unused_args.m
@@ -1635,7 +1635,7 @@ need_unify(ModuleInfo, UnusedVars, Unify, Changed) :-
         Unify = deconstruct(LVar, _, ArgVars, ArgModes, CanFail, _CanCGC),
         not list.member(LVar, UnusedVars),
         (
-            % Are any of the args unused? If so, we need to to fix up the
+            % Are any of the args unused? If so, we need to fix up the
             % goal_info.
             CanFail = cannot_fail,
             check_deconstruct_args(ModuleInfo, UnusedVars, ArgVars, ArgModes,