diff --git a/scalafmt-core/shared/src/main/scala/org/scalafmt/internal/FormatOps.scala b/scalafmt-core/shared/src/main/scala/org/scalafmt/internal/FormatOps.scala
index ef7da3a143..c52983d3f2 100644
--- a/scalafmt-core/shared/src/main/scala/org/scalafmt/internal/FormatOps.scala
+++ b/scalafmt-core/shared/src/main/scala/org/scalafmt/internal/FormatOps.scala
@@ -470,6 +470,7 @@ class FormatOps(
 
   def insideInfixSplit(
       app: Member.Infix,
+      isBeforeOp: Boolean,
       ft: FormatToken
   )(implicit style: ScalafmtConfig): Seq[Split] =
     app match {
@@ -477,9 +478,17 @@ class FormatOps(
           if style.spaces.neverAroundInfixTypes.contains(t.op.value) =>
         Seq(Split(NoSplit, 0))
       case t =>
+        def useSpace = isBeforeOp ||
+          style.spaces.beforeInfixArgInParens(app.op.value) ||
+          !(app.arg match {
+            case _: Lit.Unit => true
+            case x: Member.ArgClause if x.values.lengthCompare(1) != 0 => true
+            case x => isEnclosedInParens(x)
+          })
         val afterInfix = style.breakAfterInfix(t)
         if (afterInfix ne Newlines.AfterInfix.keep) {
-          if (ft.meta.leftOwner ne app.op) Seq(Split(Space, 0))
+          val spaceMod = Space(useSpace)
+          if (ft.meta.leftOwner ne app.op) Seq(Split(spaceMod, 0))
           else {
             val fullInfix = InfixSplits.findEnclosingInfix(app)
             val ok = isEnclosedInParens(fullInfix) || fullInfix.parent.forall {
@@ -488,13 +497,16 @@ class FormatOps(
               case _ => true
             }
             if (ok)
-              InfixSplits(app, ft, fullInfix).getBeforeLhsOrRhs(afterInfix)
-            else Seq(Split(Space, 0))
+              InfixSplits(app, ft, fullInfix)
+                .getBeforeLhsOrRhs(afterInfix, spaceMod = spaceMod)
+            else Seq(Split(spaceMod, 0))
           }
         } else {
           // we don't modify line breaks generally around infix expressions
           // TODO: if that ever changes, modify how rewrite rules handle infix
-          Seq(InfixSplits.withNLIndent(Split(getMod(ft), 0))(app, ft))
+          val mod = getMod(ft)
+          val modOrNoSplit = if (mod != Space || useSpace) mod else NoSplit
+          Seq(InfixSplits.withNLIndent(Split(modOrNoSplit, 0))(app, ft))
         }
     }
 
@@ -700,7 +712,8 @@ class FormatOps(
 
     def getBeforeLhsOrRhs(
         afterInfix: Newlines.AfterInfix,
-        newStmtMod: Option[Modification] = None
+        newStmtMod: Option[Modification] = None,
+        spaceMod: Modification = Space
     ): Seq[Split] = {
       val beforeLhs = ft.meta.leftOwner ne app.op
       val maxPrecedence =
@@ -768,7 +781,7 @@ class FormatOps(
         .withSingleLine(singleLineExpire)
         .andPolicyOpt(singleLinePolicy)
         .andPolicyOpt(delayedBreak)
-      val spaceSingleLine = Split(Space, 0)
+      val spaceSingleLine = Split(spaceMod, 0)
         .onlyIf(newStmtMod.isEmpty)
         .withSingleLine(singleLineExpire)
         .andPolicyOpt(singleLinePolicy)
@@ -799,7 +812,7 @@ class FormatOps(
           .andPolicyOpt(breakAfterClose)
           .withIndent(nlIndent)
           .withPolicy(nlPolicy)
-        val singleLineSplit = Split(Space, 0)
+        val singleLineSplit = Split(spaceMod, 0)
           .notIf(noSingleLine)
           .withSingleLine(endOfNextOp.fold(close)(_.left))
           .andPolicyOpt(breakAfterClose)
@@ -817,7 +830,7 @@ class FormatOps(
               val exclude =
                 if (breakMany) TokenRanges.empty
                 else insideBracesBlock(nextFT, expire, true)
-              Split(ModExt(newStmtMod.getOrElse(Space)), cost)
+              Split(ModExt(newStmtMod.getOrElse(spaceMod)), cost)
                 .withSingleLine(expire, exclude)
           }
         }
diff --git a/scalafmt-core/shared/src/main/scala/org/scalafmt/internal/Router.scala b/scalafmt-core/shared/src/main/scala/org/scalafmt/internal/Router.scala
index 4410c3693c..fdbe16d8b6 100644
--- a/scalafmt-core/shared/src/main/scala/org/scalafmt/internal/Router.scala
+++ b/scalafmt-core/shared/src/main/scala/org/scalafmt/internal/Router.scala
@@ -682,6 +682,8 @@ class Router(formatOps: FormatOps) {
           case Term.Name(name) =>
             style.spaces.afterTripleEquals && name == "===" ||
             (rightOwner match {
+              case _: Term.ArgClause =>
+                style.spaces.beforeApplyArgInParens(name)
               case _: Member.ParamClause =>
                 style.spaces.afterSymbolicDefs && isSymbolicName(name)
               case _ => false
@@ -1944,7 +1946,7 @@ class Router(formatOps: FormatOps) {
         Seq(
           Split(NoSplit, 0)
         )
-      case FormatToken(op @ T.Ident(_), right, _) if leftOwner.parent.exists {
+      case FormatToken(op: T.Ident, right, _) if leftOwner.parent.exists {
             case unary: Term.ApplyUnary =>
               unary.op.tokens.head == op
             case _ => false
@@ -2275,9 +2277,9 @@ class Router(formatOps: FormatOps) {
 
       // Infix operator.
       case FormatToken(_: T.Ident, _, FormatToken.LeftOwner(AsInfixOp(app))) =>
-        insideInfixSplit(app, formatToken)
+        insideInfixSplit(app, false, formatToken)
       case FormatToken(_, _: T.Ident, FormatToken.RightOwner(AsInfixOp(app))) =>
-        insideInfixSplit(app, formatToken)
+        insideInfixSplit(app, true, formatToken)
 
       // Case
       case FormatToken(_: T.KwCase, _, _)
diff --git a/scalafmt-tests/src/test/resources/unit/Apply.stat b/scalafmt-tests/src/test/resources/unit/Apply.stat
index 4393e9b15c..01d5703d1e 100644
--- a/scalafmt-tests/src/test/resources/unit/Apply.stat
+++ b/scalafmt-tests/src/test/resources/unit/Apply.stat
@@ -79,14 +79,14 @@ object a {
 >>>
 object a {
   +()
-  ===()
-  bar()
+  === ()
+  bar ()
   +(baz)
-  ===(baz)
-  bar(baz)
+  === (baz)
+  bar (baz)
   +(baz, qux)
-  ===(baz, qux)
-  bar(baz, qux)
+  === (baz, qux)
+  bar (baz, qux)
 }
 <<< #3607 beforeApplyArgInParens=never
 spaces.beforeApplyArgInParens = never
@@ -131,12 +131,12 @@ object a {
 >>>
 object a {
   +()
-  ===()
+  === ()
   bar()
   +(baz)
-  ===(baz)
+  === (baz)
   bar(baz)
   +(baz, qux)
-  ===(baz, qux)
+  === (baz, qux)
   bar(baz, qux)
 }
diff --git a/scalafmt-tests/src/test/resources/unit/ApplyInfix.stat b/scalafmt-tests/src/test/resources/unit/ApplyInfix.stat
index f076a268c5..ceba30c46f 100644
--- a/scalafmt-tests/src/test/resources/unit/ApplyInfix.stat
+++ b/scalafmt-tests/src/test/resources/unit/ApplyInfix.stat
@@ -235,15 +235,15 @@ object a {
   foo + baz
   foo === baz
   foo bar baz
-  foo + ()
-  foo === ()
-  foo bar ()
-  foo + (baz)
-  foo === (baz)
-  foo bar (baz)
-  foo + (baz, qux)
-  foo === (baz, qux)
-  foo bar (baz, qux)
+  foo +()
+  foo ===()
+  foo bar()
+  foo +(baz)
+  foo ===(baz)
+  foo bar(baz)
+  foo +(baz, qux)
+  foo ===(baz, qux)
+  foo bar(baz, qux)
 }
 <<< #3607 beforeInfixArgInParens=aftersymbolic
 spaces.beforeInfixArgInParens = aftersymbolic
@@ -269,11 +269,11 @@ object a {
   foo bar baz
   foo + ()
   foo === ()
-  foo bar ()
+  foo bar()
   foo + (baz)
   foo === (baz)
-  foo bar (baz)
+  foo bar(baz)
   foo + (baz, qux)
   foo === (baz, qux)
-  foo bar (baz, qux)
+  foo bar(baz, qux)
 }