diff --git a/packages/iconvenc/fpmake.pp b/packages/iconvenc/fpmake.pp
index 644a80635a..7acdea9080 100644
--- a/packages/iconvenc/fpmake.pp
+++ b/packages/iconvenc/fpmake.pp
@@ -19,6 +19,7 @@ begin
     P.Version:='2.7.1';
     P.Author := 'Marco van de Voort';
     P.License := 'Library: LGPL2 or later, header: LGPL with modification, ';
+    P.OSes := [beos,haiku,freebsd,darwin,iphonesim,solaris,linux];
     P.HomepageURL := 'www.freepascal.org';
     P.Email := '';
     P.Description := 'A libiconv header translation.';
diff --git a/packages/libcurl/fpmake.pp b/packages/libcurl/fpmake.pp
index 7282b526d4..d78527ab7b 100644
--- a/packages/libcurl/fpmake.pp
+++ b/packages/libcurl/fpmake.pp
@@ -21,6 +21,7 @@ begin
     P.Author := 'Library: Daniel Stenberg, header: Free Pascal development team';
     P.License := 'Library: MIT, header: LGPL with modification, ';
     P.HomepageURL := 'www.freepascal.org';
+    P.OSes := [beos,haiku,freebsd,darwin,iphonesim,solaris,netbsd,openbsd,linux];
     P.Email := '';
     P.Description := 'Library to fetch files from URLs using many protocols.';
     P.NeedLibC:= true;  // true for headers that indirectly link to libc?
diff --git a/packages/ncurses/fpmake.pp b/packages/ncurses/fpmake.pp
index 03dee1d63c..36aa5b60c4 100644
--- a/packages/ncurses/fpmake.pp
+++ b/packages/ncurses/fpmake.pp
@@ -17,6 +17,7 @@ begin
     P.Directory:='ncurses';
 {$endif ALLPACKAGES}
     P.Version:='2.7.1';
+    P.OSes := [beos,haiku,freebsd,darwin,iphonesim,solaris,netbsd,openbsd,linux];
     P.SourcePath.Add('src');
     P.IncludePath.Add('src');
 
diff --git a/packages/pthreads/fpmake.pp b/packages/pthreads/fpmake.pp
index 88695da141..c59f480c56 100644
--- a/packages/pthreads/fpmake.pp
+++ b/packages/pthreads/fpmake.pp
@@ -17,6 +17,7 @@ begin
     P.Directory:='pthreads';
 {$endif ALLPACKAGES}
     P.Version:='2.7.1';
+    P.OSes := [beos,haiku,freebsd,darwin,iphonesim,solaris,netbsd,openbsd,linux];
     P.SourcePath.Add('src');
     P.IncludePath.Add('src');
 
diff --git a/packages/users/fpmake.pp b/packages/users/fpmake.pp
index ba637fd4c9..3f430fb7a8 100644
--- a/packages/users/fpmake.pp
+++ b/packages/users/fpmake.pp
@@ -20,6 +20,7 @@ begin
     P.Author := 'Michael van Canneyt, Marco van de Voort';
     P.License := 'LGPL with modification, ';
     P.HomepageURL := 'www.freepascal.org';
+    P.OSes := [freebsd,linux];
     P.Email := '';
     P.Description := 'Headers to access Unix groups and users.';
     P.NeedLibC:= false;
diff --git a/packages/utmp/fpmake.pp b/packages/utmp/fpmake.pp
index 4493ba31ba..ac254d91e5 100644
--- a/packages/utmp/fpmake.pp
+++ b/packages/utmp/fpmake.pp
@@ -18,6 +18,7 @@ begin
 {$endif ALLPACKAGES}
     P.Version:='2.7.1';
     P.SourcePath.Add('src');
+    P.OSes := [beos,haiku,freebsd,darwin,iphonesim,solaris,netbsd,openbsd,linux];
 
     T:=P.Targets.AddUnit('utmp.pp');
 
diff --git a/packages/uuid/fpmake.pp b/packages/uuid/fpmake.pp
index 6bf49ae2e1..e141bd8ac2 100644
--- a/packages/uuid/fpmake.pp
+++ b/packages/uuid/fpmake.pp
@@ -18,6 +18,7 @@ begin
 {$endif ALLPACKAGES}
     P.Version:='2.7.1';
     P.SourcePath.Add('src');
+    P.OSes := [linux];
 
     T:=P.Targets.AddUnit('libuuid.pp');
     T:=P.Targets.AddUnit('macuuid.pp');
diff --git a/packages/x11/fpmake.pp b/packages/x11/fpmake.pp
index 69ebd31d0f..f7ea896240 100644
--- a/packages/x11/fpmake.pp
+++ b/packages/x11/fpmake.pp
@@ -17,6 +17,10 @@ begin
     P.Directory:='x11';
 {$endif ALLPACKAGES}
     P.Version:='2.7.1';
+    P.OSes:=[beos,haiku,freebsd,solaris,netbsd,openbsd,linux,os2,emx];
+    // Do not build x11 on iPhone (=arm-darwin)
+    if Defaults.CPU<>arm then
+      P.OSes := P.OSes + [darwin];
     P.SourcePath.Add('src');
     P.IncludePath.Add('src');
 
diff --git a/packages/xforms/fpmake.pp b/packages/xforms/fpmake.pp
index f2756a92ee..728b1dc37b 100644
--- a/packages/xforms/fpmake.pp
+++ b/packages/xforms/fpmake.pp
@@ -18,6 +18,11 @@ begin
 {$endif ALLPACKAGES}
     P.Version:='2.7.1';
     P.SourcePath.Add('src');
+    P.OSes := [beos,haiku,freebsd,solaris,netbsd,openbsd,linux];
+    // Do not build x11 on iPhone (=arm-darwin)
+    if Defaults.CPU<>arm then
+      P.OSes := P.OSes + [darwin];
+
     P.IncludePath.Add('src');
     P.Dependencies.Add('x11');