diff --git a/alib2data/src/regexp/formal/FormalRegExpAlternation.h b/alib2data/src/regexp/formal/FormalRegExpAlternation.h
index d1e341bee89510b4107a99e50c1aed454a6ae177..bf6852a9353a76f8a5de958605f01a660c3ce365 100644
--- a/alib2data/src/regexp/formal/FormalRegExpAlternation.h
+++ b/alib2data/src/regexp/formal/FormalRegExpAlternation.h
@@ -13,12 +13,6 @@
 
 namespace regexp {
 
-namespace simplify {
-
-class RegExpOptimize;
-
-} /* namespace simplify */
-
 /**
  * Represents alternation operator in the regular expression. Contains list of FormalRegExpElement
  * as operands of the operator.
diff --git a/alib2data/src/regexp/formal/FormalRegExpConcatenation.h b/alib2data/src/regexp/formal/FormalRegExpConcatenation.h
index fa2bb726987bf70a7a3bf9970dbcc50f579fa907..ef0e0138f53e25cfbf96bfa67848282fe7340211 100644
--- a/alib2data/src/regexp/formal/FormalRegExpConcatenation.h
+++ b/alib2data/src/regexp/formal/FormalRegExpConcatenation.h
@@ -15,12 +15,6 @@
 
 namespace regexp {
 
-namespace simplify {
-
-class RegExpOptimize;
-
-} /* namespace simplify */
-
 /**
  * Represents concatenation operator in the regular expression. Contains list of FormalRegExpElement
  * as operands of the operator.
diff --git a/alib2data/src/regexp/formal/FormalRegExpIteration.h b/alib2data/src/regexp/formal/FormalRegExpIteration.h
index 5a2e4633dcae4f782171da2907413d323785d494..e9d74a5a902a4c4a76e0d2fef34219496ced33bd 100644
--- a/alib2data/src/regexp/formal/FormalRegExpIteration.h
+++ b/alib2data/src/regexp/formal/FormalRegExpIteration.h
@@ -13,12 +13,6 @@
 
 namespace regexp {
 
-namespace simplify {
-
-class RegExpOptimize;
-
-} /* namespace simplify */
-
 /**
  * Represents iteration operator in the regular expression. Contains one FormalRegExpElement
  * as operand.